This boot is used on R model 5 Speed Transmissions from Model year 1981 on and also all K75 and K100 models. This is a common source of an oil leak and even if it's not leaking, more often than not, when disturbed, the boot will tear. Therefore, it's always a good idea to have one of these on hand whenever you have work to do in this area. If for example you are removing the transmission. Or performing a spline lube, you always run the risk of damaging the boot in the process and then you will need to get one of these before you can finish the job. We highly recommend that you also order one of these boots when replacing your clutch..
Equivalent to BMW part number 23 13 1 338 731 (23131338731)