Ensolite

Gold's Gym brand "yoga" foam; 3/8" thick

Therm-a-seat, a common incarnation of ensolite foam.

This is the BAD foam.

Ensolite, also known as marine foam, is a squishy, rubbery, closed-cell foam. It is often used when making stabbing tips and low profile spears.

It can be most commonly found in the form of Gold's Gym yoga mats (picture to the right), therm-a-seats, some gardening knee cushions, lifeguard tubes, and nerf footballs (not to be confused with poof footballs). Most sports stores and stores with a sporting/exercise department will have a comparable exercise mat.

Wal-Mart carries yoga mats for a little under $20. Many sporting goods/outdoor stores will carry therm-o-seats, usually for under $7 or so. Often times, you can salvage old lifeguard tubes from YMCAs and other institutions. If you ask if you may have any they are going to discard, usually they will give them to you.

Depending on the weapon type, build, and thickness of the ensolite, you may need to use more than one layer of ensolite. A decent rule of thumb (assuming 3/8" thick foam) is blues need one layer, reds two, and (low-profile) spears use four or more. Using too much can cause tip wobble/destabilization, however.

Bad Yoga Foam

There is also a type of yoga pad one should avoid. It is very thin (6mm/quarter-inch or less) and often covered entirely covered with small bump texture. This foam is filled with hate and makes things hit harder (or just plain fail); you should avoid this foam and not use it in place of anything above.