Therapy Putty, 6 oz, Extra Firm, Gray. Bleed proof, nontoxic, clean and non-oily, Therapy Putty leaves no residue and wont fragment. Putty can be squeezed, stretched, twisted or pinched to meet a wide range of strengthening needs, or used to encourage heel strike and strengthen foot muscles. Combine colors to create custom resistance to meet individual needs. Nontoxic. Latex free.