Promax QR-1 Seatpost Clamp - 34.9mm, QR, BlackQR 1 seatpost clamps are cold forged and CNC machined from 6061 T6 aluminum alloy. The QR 1, as the name implies, has a quick release lever, making seat height adjustments a snap. Weighing just 30 grams 1. 1 ounces in the 31. 8 size, its as lightweight as it is tough. The head of the lever and the face of the clamp are given a proprietary low friction surface treatment that ensures smooth lever action for the life of the clamp without the need for a