PICTURES ARE REPRESENTATIVE OF ITEM, BUT ARE NOT OF THE ACTUAL ITEM. Product dimensions, finish, head markings, thread length, stamping shape or forging shape, etc., may differ from picture. Products are guaranteed to meet the specifications to which they are manufactured. Specifications allow for tolerances in dimension and shape, which can vary from lot to lot. More economical and easier to install than other heavy duty nuts for blind side applications. Free floating nut will compensate for poorly aligned holes. The square cage design keeps the nut from rotating during tightening. Cage nuts are successfully used in heavy duty farm machinery, rail cars, home entetainment components and heating equipment among other applications. . Steel: Cage: SAE 1050 - 1065 spring steel Nut: 6-32 thru 1/4-20: SAE 1108 or equivalent steel 5/16-18 & 3/8-16: SAE 1018 or equivalent steel 1/2-13: SAE 1108 or equivalent steel. Stainless: Cage: Class 304 3/4-hard, stainless steel Nut: Class 304 J3 stainles, steel.