Unifit Metalloys offers superior ASTM A563 Grade DH hex nuts—quenched and tempered carbon steel heavy-hex nuts engineered for exceptional strength in structural applications. Ideal for use with A325 or A490 structural bolts, these nuts deliver a proof load stress of 175 ksi (150 ksi when galvanized), with hardness ranging from C24 to C38 Rockwell. Manufactured to comply with ASTM A563... https://www.unifitmetalloys.com/blog/astm-a325-type-1-bolts-a563-hex-nuts/