Specialized has long offered their Airlock tubes for cyclists who ride clincher tires, can't stand dealing with punctures and just prefer the simplicity of a self-healing tube. Airlock Tubes come prepared with a homogenous sealant already installed. The non-toxic formula is more like a gel than most sealants, and is developed not to separate or dry out. It is highly effective for small punctures and works continuously to prevent slow leaks.