The Allen bolt version of theFlip-Lock. The Lip-Lock seat collar features a 15mm height for a better grip to securely hold the seatpost into the frame. A hardend bolt and stainless steel pivot allow tight and even clamping pressure. Tightens with a 5mm Allen wrench. Very nicely made and compares to seat collars costing ten bucks more. Select 32mm or 35mm.