(hint #1) Being able to play whatever I want has been a central theme to my own discovering how to play guitar. I've been on that path for 37 years, and it's enabled me to uncover, test and refine a unique, skill generating learning approach.
It is important to note that urethane foam is most commonly used to refer to a material made from polyurethane. The urethane reference in this name is to the type of links, also known as carbamates, that join the units in polyurethane.
Urethane has a far wider scope of applications than vinyl. This is because urethane is an actual base chemical and vinyl is a chemical byproduct. For example, polyesters, polyethers, diisoyanates and glycols are urethane-based materials.