SHIMANO BR-R451 Mid-Reach Rim Brake Calipers 

Compatible with STI and brake levers that are Super SLR enabled (e.g. Dura Ace Di2 7970, Dura-Ace 7900, Ultegra Di2 6770, Ultegra 6700, 105 5700, Tiagra 4600)
Light action and accurate brake power
Adjustable toe-in brake shoes
Use of these calipers with standard SLR-enabled STI and brake levers results in a mushy brake response

Max tire size: 32mm
Brake Type: Rim Brake
Brake Lever Pull: Short Pull
Brake Mechanism: Side Pull (Dual-Pivot)
Mount Type: Mid Reach Caliper (47 - 57mm)
Front/Rear Specific: Yes

Original Shimano parts guarantee that all components work perfectly for optimum performance and maximum safety and longevity.