They're called pipe screens & are designed to keep the tobacco &/or ash(usually finely textured stuff) from slipping through & getting sucked into your mouth. Second question,m yeah, absolutely. You can pick them up either at head or vape shops, or a number of the online tobacco suppliers like smokingpipes.com, pipesand igars.com, or coupojoes, etc.
let's not be presumptuous here. Well, you can but I'm not
The first pipe I bought had a metal basket in the chamber. I wanted a cheap pipe (for smoking pipe tobacco) and simply didn't know any better.
Seems to be a bit of confusion as to what the OP is talking about, though.
I'm talking about these, but I'm not sure the OP is.