Animal Seat with that mcneil patented design of attaching to the post, eg by an allen key that go's through the top of the seat to bolt it directly to the post. Both the seat and post have sexed splined contours so you can angle the seat and it should'nt slip at all. You cant move the seat forward or back as there are no rails, but fixed central should be cool for everyone but the most finnicky of you out there. Laterz