TPU stands for thermoplastic polyurethane, which is a hard-toe cap that some boots use in lieu of steel. This type of toe cap is much lighter than steel, reducing the overall weight of the boot. TPU caps won't set off metal detectors and offer electrical resistance for those who may be working around live wiring. A composite cap also provides better thermal insulation for those working in cold environments. That said, it’s important to understand that TPU caps do not offer the same level of crush or puncture protection as boots with steel caps.