Salsa Guide Carbon Seatpost 31.6 x 400mm 18mm Offset BlackSalsa Guide Carbon Seatpost 31. 6 x 400mm 18mm Offset Black. The Guide Carbon Seatpost features a highly adjustable two bolt head design while remaining lightweight durable and supportive when you need it most. Unidirectional carbon fiber shaft Bonded Aluminum two bolt adjustable head TECH SPECS Defined Color Black Weight 263 Offset (mm) 18 Diameter 31. 6 Color Black Material Carbon Clamp Style Standard Rails Length 400