Park tool shop hammer hmr4the perfect shop hammerdesigned and built specifically for bicycle work the hmr 4 has a fiberglass shaft a soft touch rubber grip and a two sided headsteel on one side and a replaceable plastic head part 293 on the other sidefeatures13 5 long 345mmsteel striking face 1 38 35mm diameterplastic face 1 1116 43mm diameter24 ounce head 680gbuypark tool toolsfrom chain reaction cycles the worlds largest online bike store