Are molded from pliable rubber in two kidney shapes. They are used for smoothing, shaping and finishing pieces. The blue are very flexable, and the black colored rib are a bit more rigid. FR FRSS Soft, 3 1/8". FRSSRegular price: $6.89Sale price: $5.51 FRSO Soft, 4 1/4". FRSORegular price: $6.89Sale price: $5.51 FRSM Hard, 3 1/8". FRSMRegular price: $6.89Sale price: $5.51 FRH Hard, 4 1/4". FRHRegular price: $6.89Sale price: $5.51