Cheap, but they shoot a little low for my liking. - Angry Bear Arms Low Profile Serrated Small Frame Pistol Sights

They're steel, they work fine. The exterior is either coated or painted black, but it is sufficiently tough. The only problem I have is they shoot quite low. That may just be my gun, it's not an OEM Glock, but the POI is about 3/4 of the way down the front blade when the top of the blade and rear sight are aligned and flush. I don't like "combat style" that much because the POI occludes the target, and this is a little worse than that. Smaller steel plates past 30 or so yards start disappearing into the sight picture and I sometimes have to move the gun around to see what I'm supposed to be shooting.