Padded version of the original P Rail seat with tough Kevlar cover. The S&M P-rail seat is designed to work with the S&M P-guts and a regular pivotal seat post. The rails on the seat allow it to be moved forwards or backwards on the guts before attaching to the pivotal post to allow for adjustment of your seat position - this is genius if you find your regular pivotal system puts your seat too far forward. According to S&M this seat has been tested using the boniest arses in the company and is as comfortable as it gets. Alternatively, this can be used as a regular railed seat with any regular seat post that accepts 8mm rails. N.B Do not buy for use with a pivotal seat post unless you are also using S&M P-Guts