Provide comfort and pain relief by safely removing callus with Beta-Hydroxy. Cushlin Ultra Slim Callus Removers use Salicylic Acid, a Beta-Hydroxy Acid, to gently and safely remove callus; stick instantly to skin and stay in place for 2 days; won't catch on hosiery. Thin, flexible cushions conform to shape of foot. Nearly invisible, water-resistant protection.