diff --git a/src/script/script.h b/src/script/script.h
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -403,6 +403,12 @@
     int64_t m_value;
 };
 
+/**
+ * We use a prevector for the script to reduce the considerable memory overhead
+ * of vectors in cases where they normally contain a small number of small
+ * elements. Tests in October 2015 showed use of this reduced dbcache memory
+ * usage by 23% and made an initial sync 13% faster.
+ */
 typedef prevector<28, uint8_t> CScriptBase;
 
 /** Serialized script, used inside transaction inputs and outputs */