Different bikes sometimes have different seatpost diameters. The ShockStop Endurance Suspension Seatpost is available in 27.2mm, 30.4mm, 30.9mm, and 31.6mm diameters along with 280, 350, 400, and 450mm lengths. If your bike's seatpost diameter does not match one of these standards, you'll need a shim to adapt our seatpost to your bike's frame.  Don't worry though, the shims are super-lightweight and essentially invisible once installed.

Not sure what size seatpost you have currently?  There are a couple different ways to find out.

• Most seatposts have the diameter printed somewhere near the bottom of the post.  You'll need to remove the seatpost from the bike frame (mark your existing seatpost height with a bit of tape before you remove it so you can replace it easily), and look for a number like 27.2, 30.9, or 31.6 (etc.).  That is the diameter of the post.
• If you know the make, model, and year of your bike, you may be able to look up the seatpost diameter online.  Feel free to shoot us an email at support@redshiftsports.com - we'll see if we can help out.
• Ask your local bike shop - they'll be able to accurately measure your bike's seatpost.

Non-compatible posts:  Unfortunately, if your bike's seatpost is smaller than 27.2mm (for example, the 25.4mm posts found on some recent model Cannondale Synapses) our seatpost is currently not compatible with your bike.  Likewise, if you have a bike with an aero/oval/non-round seatpost, or if your bike has an integrated seatmast, the seatpost is also not compatible.