Enjoying a smooth and comfortable ride on your Brompton is all about the tiny details. Our Replacement Seatpost O-rings stop the Pentaclip clunking on the frame when the Seatpost is put in the fully down position, which helps to reduce damage and general wear and tear that occurs from lowering the seat. O-rings go around the top of your Brompton seatpost right beneath the Pentaclip and are easy to install. They act as a barrier between the Pentaclip which stops it from hitting the painted main frame when you collapse the seatpost quickly and without control. They may be small but they're an essential part of keeping your Brompton looking new and fresh, so if yours are worn out or you don't have them, treat your Brompton to a pair of our replacement O-rings and install in minutes.