What type of foam for eyepiece cases?

I need to replace some foam in one of my eyepiece cases. I've heard that some foam should not be used due to outgassing. Which type is safe?

Thanks,

Joe

I use Polyethylene and polyurethane. They both seem stable and non-gassing. Polyehtylene is stiff compared to polyurethane and it cuts easier too.

http://www.mcmaster.com/

You can find both here.

Floyd

Thanks for the replies and the pics. Now off to see how much the stuff costs.

Joe