Tektro R539 Recessed Nut Road Caliper Set The R539 is an excellent dual-pivot caliper brake for road bikes. Made of forged aluminum arms, this caliper is solid, yet only weighs in at 160 grams each. The R539 features Tektro's new lock device QR. Standard calipers don't open very wide. Therefore, it is hard to get wider tires out. However, Tektro has increased the width that it opens as well as added on a safety lock device. Dual Pivot Caliper Forged aluminum arms P422 adjustable angle cartridge brake pads Dimensions: 47-57mm Recessed Nut160 grams per | Tektro | R539 Road Caliper Set | Black | 47-57Mm