C4 Collars are ultra-durable and mega-comfortable.  Made of medical grade thermo-elastomer, C4 collars are non-porous which makes them waterproof, stain resistant, hypoallergenic, and easily washable. Most Collars stay wet and are like sponges for dirt, grime, and bacteria. They stink, look dirty and cause skin irritations. Not C4.  Our collars are stink proof, too.