Comparison : Item # 4501R, 3/8" x 18mm x 1.50 (O-ring) High Pressure Repair Line (4")
Item # 4502R, 3/8" x 16mm x 1.50 (O-ring) High Pressure Repair Line (4")
Item # 4503R, 3/8" x 16mm x 1.50 (O-ring) High Pressure Repair Line (4")
Item # 4504R, 3/8" x 5/8" - 18 (O-ring) High Pressure Repair Line (4")
Item # 4505R, 5/16" x 5/8" - 18 (O-ring) High Pressure Repair Line (4")