Comparison : Item # 111-059-4, 1/4 Inch Stem O.D. Push-To-Connect Plug
Item # 111-059-5, 5/16 Inch Stem O.D. Push-To-Connect Plug
Item # 111-059-6, 3/8 Inch Stem O.D. Push-To-Connect Plug
Item # 111-059-8, 1/2 Inch Stem O.D. Push-To-Connect Plug