Fire Eye's meaty double-bolt seat clamp is certainly burly - all 1.04kg of it. The clamp keeps the post locked in position during even the heaviest landings and it's good value, although it only comes in a 29.8mm size.
Forged from 6061 T-6 aluminium alloy, Woodman's Death Grip QR weighs 45g and is available in 28.6, 29.8, 31.8 and 34.9mm sizes. It's easy to use and well made, with a positive cam action. The only negative is that baggy shorts can