This saddle is identical in size to the b66 s however it is mounted on a single rather than a double rail so you can have the brooks comfort on a bicycle fitted with the more modern micro adjust seat post a single rail frame also gives a slightly reduced spring effect over the twin railed b66 savailable in black antique brown shown and honeydont forget to use proofide regularily to ensure maximum comfort and longevity of your saddle you can purchase the recently launched brooks ma