Racetech - Alloy Back Bracket (RTB2115B)RTB2115B: Racetech 5mm aluminium (5083) bracket for back mounting seats. This bracket bolts to the shoulder beam of Racetech 119 and 4100 Series seats and typically works in conjunction with RTB2005C clamps, allowing you to fix the seat to the lateral diagonal rollcage tube. Requires four holes drilled to bolt on the clamps once you have your seat set up in the optimum driving position. Compatible with the following Racetech seats: RT4100, RT4100T,