These are rush order custom square u bolts made domestically using 304 stainless steel material. We had 50 pieces manufactured for our customer at just 3 days production time to be shipped next day air directly to the job site. Material certs and a certificate of conformance was provided per our customer's specific instruction. The inside width was set at 4 inches, inside depth at 9 inches, with approximately 2 inches of 3/8 coarse thread on each leg.