Always has the right replacement parts at a fair price
Cheap, convenient and easy-to-use. Sure beats me cutting the darned sponges myself - one less hassle for me. Trust me, I've had a lot of sponges in my life - and these are truly an asset to have.
I consider it a necessary tool when grinding class. The 'L' shape allows you to use just 1 sponge. Some of my grinding wheels are of the pedestal shape, where the grinding portion is above the flat base of the grinder. All you have to do is invert the sponge to keep the wheel damp.