diff --git a/blocks/blockstore/caching.go b/blocks/blockstore/caching.go
new file mode 100644
index 000000000..5657059d8
--- /dev/null
+++ b/blocks/blockstore/caching.go
@@ -0,0 +1,16 @@
+package blockstore
+
+// Next to each option is it aproximate memory usage per unit
+type CacheOpts struct {
+	HasBloomFilterSize   int // 1 bit
+	HasBloomFilterHashes int // No size, 7 is usually best, consult bloom papers
+	HasARCCacheSize      int // 32 bytes
+}
+
+func DefaultCacheOpts() CacheOpts {
+	return CacheOpts{
+		HasBloomFilterSize:   512 * 8 * 1024,
+		HasBloomFilterHashes: 7,
+		HasARCCacheSize:      64 * 1024,
+	}
+}