It depends on the polymer. I used the chlorinated brake cleaner that can't be used at the car dealerships on my Glock w/o a problem. But I once sprayed the same stuff on a Motorola 2-way radio battery, & it melted. However, while the non-chlorinated brake cleaner is safe for the atmosphere, it's a much more harsh cleaner, & I would never use it on any polymer. Just read the ingredients on the can. While I do use the chlorinated cleaner on the metal parts, I do not spray it on the polymer parts any more. So the slide & barrel get a good hosing of brake cleaner, but not the plastic lower. GARY