My understanding is that these are added to the slide as an "fix" for sticking older slides and are a normal bmw part, etc. I got a pair from hucky ($1.70 each or something) and installed them because I sometimes am not having my idle return to base when I stop. Now once installed it seems to rob some of the "top end" power, and that highway speed "roll the throttle to pass" power is gone. I dont see how the slides can even move with them in place. Going to take them out, but figured I would post up to see what everyone else has experienced and/or educate others that might be conidering it as a fix. Just as an additional, I replaced my slide needles at the same time.