These stainless steel pipe screens serve two purposes, the first is to prevent the formation of dottle, the nasty wet tobacco that can ruin pipes, and the second is preventing hot embers and tobacco from going up your pipe shaft and into your mouth. These pipe screens have a diameter of 0.625 inches.
Thanks to Pipeee, I'll never have to go to the damn local "Smoke Shop" to pay too much for five crappy brass screens again, EVER. These screens are high quality, very sturdy and long-lasting. Don't buy screens anywhere else.