closed cell foam
Normally I can fish a single popper all day without it sinking.
All foam is not created equal.*G* Some flip flops are made of a foam
rubber type material, a bit heavier and more absorbant than the
closed cell foam that seems to work far better.
Words of wisdom . I can run my finger over the edge of foam for a little rough feel and rough look to the foam for closed cell. I don't even give it another look if its foam rubber smooth. Some are in between, a little rough and a little smooth (with more or less of both kinds of foam). I just try to find the stuff that has at least some roughness to it. As cheap and easy as foam flies or foam poppers are to make, I just tie another one on the leader . I don't care so much if I lose one or it gets so battered that I can't use it anymore. Like Jim, I usually can catch a lot of fish before one foam popper will no longer work. They are soft bodied and not as durable but I tie them knowing that anyway. If I want durable, I tie a hard bodied balsa popper on the leader.
Robert B. McCorquodale
"Flip a fly"