The 010-9101-0403 was designed to fit into Telect's Ultra-Thin DSX-3 Chassis (P/N 010-0000-x801), so it is .70" wide. The 010-9101-0450 was designed to fit into Telect' Wide Body DSX-3 chassis (P/N 010-0000-185x), so it is .86" wide. The two modules are not interchangeable.