1/2" & 5/8", Barbell Receiver Pin Lock, Stainless Steel Sleeve Turns This Single Unit To Fit Both Receiver Sizes 1/2 " Or 5/8", Straight Barbell Style Pin Provides Function & A Lock At End Of The Unit Provides Protection All In In 1 Unit, All Weather Cap Protects Keyway From The Harsh Elements, K1 Key Blank.