Shimano tiagra r451 road brake calipershimano r451 provide good value components that will last this drop front caliper brake is no exception featuresgood value 57mm drop front caliper brakesuper slr dual pivot design keeps operating friction to a minimum improving braking performancemust be used in conjunction with st 4600 st 4603 st 5700 st 5703 st 6700 or st 7900 stisfor correct leverage ratioenhanced brake arch proportions give a quicker linear response and increased power57mm droplig