Racetech - Alloy Clamps (RTB2005C)RTB2005C Racetech aluminium clamps for back mounting seats. Precision cut from a 20mm thick 5083 alloy sheet. Sold as a pair these clamps fix around a rollcage tube and bolt to the RTB2115B or RTB3115B bracket. This allows you to effectively back mount a Racetech 119 or 4100 Series seat to the chassis rollcage at the shoulder level. Supplied with 2x M8 bolts and 2x flat washers. Size Chart: Part Tube Diameter (mm) Tube Diameter (inch) RTB2005C38 38.