There's a left and right part number for the BMW black seat bracket but if you're not using the OEM fire extinguisher, either will be fine. The two holes to mount the extinguisher are simply offset slightly one way or the other. The original fire extinguisher used to be supplied by Kidde now discontinued in Australia however a good option is Quell's with dual metal strap which is CAMS track approved. Few hints: seat mount bracket can be bought at ECS Tuning including screws. Don't use E46 instructions as it suggests tapping holes in seat. The E88 and E92 sport seats require no tapping. The screws are Trilobe thread forming and require light force and rotation to mount. Do not overtighten. Do not remove seats or electrical harnesses as others have recommended as I simply raised the seat to highest position and used a small 1/4" drive socket set. Need 10mm socket, T30 Torx male bit and approximately 2" extension. Fitted in about 12 minutes. Can mount to either front seat on preference.