'Torquer' velocity stack. 1 3/4" outer mounting diameter, 30.5mm center to center bolt hole spacing, 3/4" inner bore. Fits Zenoah G23LH / G2D / G43L / G230RC / G260RC / G231PUH / G260PUH / G260PU / G231PUM / G260PUM / G62PU engines. Also fits Chung Yang CY23RC / CY26RC / CY27RC / CY29RC / GP290 / GP420 engines. Fits Walbro WA / WT / WYK / HDA style carburetors