diff --git a/HISTORY.md b/HISTORY.md
index 19e903d64..38ce20baa 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -52,13 +52,14 @@
     cache_index_and_filter_blocks=1 or partition_filters=1).
     * bits_per_key >= 0.5 and < 1.0 is still rounded up to 1.0 (for 62% FP
     rate)
+  * Remove class definitions for FilterBitsBuilder and FilterBitsReader from
+    public API, so these can evolve more easily as implementation details.
+    Custom FilterPolicy can still decide what kind of built-in filter to use
+    under what conditions.
   * Also removed deprecated functions
-    * FilterBitsBuilder::CalculateNumEntry()
     * FilterPolicy::GetFilterBitsBuilder()
     * NewExperimentalRibbonFilterPolicy()
   * Remove default implementations of
-    * FilterBitsBuilder::EstimateEntriesAdded()
-    * FilterBitsBuilder::ApproximateNumEntries()
     * FilterPolicy::GetBuilderWithContext()
 * Remove default implementation of Name() from FileSystemWrapper.
 * Rename `SizeApproximationOptions.include_memtabtles` to `SizeApproximationOptions.include_memtables`.
diff --git a/include/rocksdb/filter_policy.h b/include/rocksdb/filter_policy.h
index 311974482..d8fb33641 100644
--- a/include/rocksdb/filter_policy.h
+++ b/include/rocksdb/filter_policy.h
@@ -38,83 +38,9 @@ class Slice;
 struct BlockBasedTableOptions;
 struct ConfigOptions;
 
-// A class that takes a bunch of keys, then generates filter
-class FilterBitsBuilder {
- public:
-  virtual ~FilterBitsBuilder() {}
-
-  // Add a key (or prefix) to the filter. Typically, a builder will keep
-  // a set of 64-bit key hashes and only build the filter in Finish
-  // when the final number of keys is known. Keys are added in sorted order
-  // and duplicated keys are possible, so typically, the builder will
-  // only add this key if its hash is different from the most recently
-  // added.
-  virtual void AddKey(const Slice& key) = 0;
-
-  // Called by RocksDB before Finish to populate
-  // TableProperties::num_filter_entries, so should represent the
-  // number of unique keys (and/or prefixes) added, but does not have
-  // to be exact. `return 0;` may be used to conspicuously indicate "unknown".
-  virtual size_t EstimateEntriesAdded() = 0;
-
-  // Generate the filter using the keys that are added
-  // The return value of this function would be the filter bits,
-  // The ownership of actual data is set to buf
-  virtual Slice Finish(std::unique_ptr<const char[]>* buf) = 0;
-
-  // Similar to Finish(std::unique_ptr<const char[]>* buf), except that
-  // for a non-null status pointer argument, it will point to
-  // Status::Corruption() when there is any corruption during filter
-  // construction or Status::OK() otherwise.
-  //
-  // WARNING: do not use a filter resulted from a corrupted construction
-  virtual Slice Finish(std::unique_ptr<const char[]>* buf,
-                       Status* /* status */) {
-    return Finish(buf);
-  }
-
-  // Verify the filter returned from calling FilterBitsBuilder::Finish.
-  // The function returns Status::Corruption() if there is any corruption in the
-  // constructed filter or Status::OK() otherwise.
-  //
-  // Implementations should normally consult
-  // FilterBuildingContext::table_options.detect_filter_construct_corruption
-  // to determine whether to perform verification or to skip by returning
-  // Status::OK(). The decision is left to the FilterBitsBuilder so that
-  // verification prerequisites before PostVerify can be skipped when not
-  // configured.
-  //
-  // RocksDB internal will always call MaybePostVerify() on the filter after
-  // it is returned from calling FilterBitsBuilder::Finish
-  // except for FilterBitsBuilder::Finish resulting a corruption
-  // status, which indicates the filter is already in a corrupted state and
-  // there is no need to post-verify
-  virtual Status MaybePostVerify(const Slice& /* filter_content */) {
-    return Status::OK();
-  }
-
-  // Approximate the number of keys that can be added and generate a filter
-  // <= the specified number of bytes. Callers (including RocksDB) should
-  // only use this result for optimizing performance and not as a guarantee.
-  virtual size_t ApproximateNumEntries(size_t bytes) = 0;
-};
-
-// A class that checks if a key can be in filter
-// It should be initialized by Slice generated by BitsBuilder
-class FilterBitsReader {
- public:
-  virtual ~FilterBitsReader() {}
-
-  // Check if the entry match the bits in filter
-  virtual bool MayMatch(const Slice& entry) = 0;
-
-  // Check if an array of entries match the bits in filter
-  virtual void MayMatch(int num_keys, Slice** keys, bool* may_match) {
-    for (int i = 0; i < num_keys; ++i) {
-      may_match[i] = MayMatch(*keys[i]);
-    }
-  }
-};
+// As of RocksDB 7.0, the details of these classes are internal
+class FilterBitsBuilder;
+class FilterBitsReader;
 
 // Contextual information passed to BloomFilterPolicy at filter building time.
 // Used in overriding FilterPolicy::GetBuilderWithContext(). References other
@@ -154,20 +80,11 @@ struct FilterBuildingContext {
   TableFileCreationReason reason = TableFileCreationReason::kMisc;
 };
 
-// We add a new format of filter block called full filter block
-// This new interface gives you more space of customization
-//
-// For the full filter block, you can plug in your version by implement
-// the FilterBitsBuilder and FilterBitsReader
-//
-// There are two sets of interface in FilterPolicy
-// Set 1: CreateFilter, KeyMayMatch: used for blockbased filter
-// Set 2: GetFilterBitsBuilder, GetFilterBitsReader, they are used for
-// full filter.
-// Set 1 MUST be implemented correctly, Set 2 is optional
-// RocksDB would first try using functions in Set 2. if they return nullptr,
-// it would use Set 1 instead.
-// You can choose filter type in NewBloomFilterPolicy
+// Determines what kind of filter (if any) to generate in SST files, and under
+// which conditions. API users can create custom filter policies that
+// defer to other built-in policies (see NewBloomFilterPolicy and
+// NewRibbonFilterPolicy) based on the context provided to
+// GetBuilderWithContext.
 class FilterPolicy {
  public:
   virtual ~FilterPolicy();
@@ -177,9 +94,9 @@ class FilterPolicy {
   // policy string.
   // The value describes the FilterPolicy being created.
   // For BloomFilters, value may be a ":"-delimited value of the form:
-  //   "bloomfilter:[bits_per_key]:[use_block_based_builder]",
-  //   e.g. ""bloomfilter:4:true"
-  //   The above string is equivalent to calling NewBloomFilterPolicy(4, true).
+  //   "bloomfilter:[bits_per_key]",
+  //   e.g. ""bloomfilter:4"
+  //   The above string is equivalent to calling NewBloomFilterPolicy(4).
   static Status CreateFromString(const ConfigOptions& config_options,
                                  const std::string& value,
                                  std::shared_ptr<const FilterPolicy>* result);
@@ -191,20 +108,20 @@ class FilterPolicy {
   virtual const char* Name() const = 0;
 
   // Return a new FilterBitsBuilder for constructing full or partitioned
-  // filter blocks. The configuration details can depend on the input
-  // FilterBuildingContext but must be serialized such that FilterBitsReader
-  // can operate based on the block contents without knowing a
-  // FilterBuildingContext.
-  // Change in 7.0 release: returning nullptr indicates "no filter"
+  // filter blocks, or return nullptr to indicate "no filter". Custom
+  // implementations should defer to a built-in FilterPolicy to get a
+  // new FilterBitsBuilder, but the FilterBuildingContext can be used
+  // to decide which built-in FilterPolicy to defer to.
   virtual FilterBitsBuilder* GetBuilderWithContext(
       const FilterBuildingContext&) const = 0;
 
   // Return a new FilterBitsReader for full or partitioned filter blocks.
   // Caller retains ownership of any buffer pointed to by the input Slice.
+  // Custom implementation should defer to GetFilterBitsReader on any
+  // built-in FilterPolicy, which can read filters generated by any other
+  // built-in FilterPolicy.
   virtual FilterBitsReader* GetFilterBitsReader(
-      const Slice& /*contents*/) const {
-    return nullptr;
-  }
+      const Slice& /*contents*/) const = 0;
 };
 
 // Return a new filter policy that uses a bloom filter with approximately
diff --git a/table/block_based/filter_policy_internal.h b/table/block_based/filter_policy_internal.h
index 4db0389f6..39fc4104e 100644
--- a/table/block_based/filter_policy_internal.h
+++ b/table/block_based/filter_policy_internal.h
@@ -18,7 +18,84 @@
 
 namespace ROCKSDB_NAMESPACE {
 
-class Slice;
+// A class that takes a bunch of keys, then generates filter
+class FilterBitsBuilder {
+ public:
+  virtual ~FilterBitsBuilder() {}
+
+  // Add a key (or prefix) to the filter. Typically, a builder will keep
+  // a set of 64-bit key hashes and only build the filter in Finish
+  // when the final number of keys is known. Keys are added in sorted order
+  // and duplicated keys are possible, so typically, the builder will
+  // only add this key if its hash is different from the most recently
+  // added.
+  virtual void AddKey(const Slice& key) = 0;
+
+  // Called by RocksDB before Finish to populate
+  // TableProperties::num_filter_entries, so should represent the
+  // number of unique keys (and/or prefixes) added, but does not have
+  // to be exact. `return 0;` may be used to conspicuously indicate "unknown".
+  virtual size_t EstimateEntriesAdded() = 0;
+
+  // Generate the filter using the keys that are added
+  // The return value of this function would be the filter bits,
+  // The ownership of actual data is set to buf
+  virtual Slice Finish(std::unique_ptr<const char[]>* buf) = 0;
+
+  // Similar to Finish(std::unique_ptr<const char[]>* buf), except that
+  // for a non-null status pointer argument, it will point to
+  // Status::Corruption() when there is any corruption during filter
+  // construction or Status::OK() otherwise.
+  //
+  // WARNING: do not use a filter resulted from a corrupted construction
+  // TODO: refactor this to have a better signature, consolidate
+  virtual Slice Finish(std::unique_ptr<const char[]>* buf,
+                       Status* /* status */) {
+    return Finish(buf);
+  }
+
+  // Verify the filter returned from calling FilterBitsBuilder::Finish.
+  // The function returns Status::Corruption() if there is any corruption in the
+  // constructed filter or Status::OK() otherwise.
+  //
+  // Implementations should normally consult
+  // FilterBuildingContext::table_options.detect_filter_construct_corruption
+  // to determine whether to perform verification or to skip by returning
+  // Status::OK(). The decision is left to the FilterBitsBuilder so that
+  // verification prerequisites before PostVerify can be skipped when not
+  // configured.
+  //
+  // RocksDB internal will always call MaybePostVerify() on the filter after
+  // it is returned from calling FilterBitsBuilder::Finish
+  // except for FilterBitsBuilder::Finish resulting a corruption
+  // status, which indicates the filter is already in a corrupted state and
+  // there is no need to post-verify
+  virtual Status MaybePostVerify(const Slice& /* filter_content */) {
+    return Status::OK();
+  }
+
+  // Approximate the number of keys that can be added and generate a filter
+  // <= the specified number of bytes. Callers (including RocksDB) should
+  // only use this result for optimizing performance and not as a guarantee.
+  virtual size_t ApproximateNumEntries(size_t bytes) = 0;
+};
+
+// A class that checks if a key can be in filter
+// It should be initialized by Slice generated by BitsBuilder
+class FilterBitsReader {
+ public:
+  virtual ~FilterBitsReader() {}
+
+  // Check if the entry match the bits in filter
+  virtual bool MayMatch(const Slice& entry) = 0;
+
+  // Check if an array of entries match the bits in filter
+  virtual void MayMatch(int num_keys, Slice** keys, bool* may_match) {
+    for (int i = 0; i < num_keys; ++i) {
+      may_match[i] = MayMatch(*keys[i]);
+    }
+  }
+};
 
 // Exposes any extra information needed for testing built-in
 // FilterBitsBuilders
diff --git a/table/block_based/full_filter_block.h b/table/block_based/full_filter_block.h
index 0068e0f4d..63d407dd5 100644
--- a/table/block_based/full_filter_block.h
+++ b/table/block_based/full_filter_block.h
@@ -12,11 +12,11 @@
 #include <string>
 #include <vector>
 
-#include "rocksdb/filter_policy.h"
 #include "rocksdb/options.h"
 #include "rocksdb/slice.h"
 #include "rocksdb/slice_transform.h"
 #include "table/block_based/filter_block_reader_common.h"
+#include "table/block_based/filter_policy_internal.h"
 #include "table/block_based/parsed_full_filter_block.h"
 #include "util/hash.h"
 
diff --git a/table/block_based/parsed_full_filter_block.cc b/table/block_based/parsed_full_filter_block.cc
index 3e555387e..9184a48d2 100644
--- a/table/block_based/parsed_full_filter_block.cc
+++ b/table/block_based/parsed_full_filter_block.cc
@@ -5,7 +5,8 @@
 //
 
 #include "table/block_based/parsed_full_filter_block.h"
-#include "rocksdb/filter_policy.h"
+
+#include "table/block_based/filter_policy_internal.h"
 
 namespace ROCKSDB_NAMESPACE {