Interlock balls and ball mounts act as a 1 wrench tightening system when used together. Standard hitch balls and ball mounts may also be used with interlock products but require 2 wrenches for installation. Ball mount measurements: Length equals the distance from the center of the ball hole to the center of the pin hole. Drop equals the distance from the top of the shank to the top of the ball platform. Rise equals the distance from the top of the ball platform to the top of the shank. No. 21901: Receiver Opening Size: 1-1/4", Hitch Ball Hole Size: 3/4", Length: 9", Drop: 1-1/4", Rise: 3/4", Capacity: 300 TW /3500 GTW, Finish: Metal Shield, Pkg Qty: 1 No. 21900: Receiver Opening Size: 1-1/4", Hitch Ball Hole Size: 3/4", Length: 7", Drop: 2-1/2", Rise: 2", Capacity: 300 TW /3500 GTW, Finish: Metal Shield, Pkg Qty: 1 No. 21792: Receiver Opening Size: 2" x 2", Hitch Ball Hole Size: 1", Length: 9", Drop: 2", Rise: 3/4", Capacity: 600 TW /6000 GTW, Finish: Metal Shield, Pkg Qty: 1 No. 21793: Receiver Opening Size: 2" x 2" x 2", Hitch Ball Hole Size: 1", Length: 9-1/2", Drop: 3-1/4", Rise: 2", Capacity: 500 TW /5000 GTW, Finish: Metal Shield, Pkg Qty: 1 No. 21794: Receiver Opening Size: 2" x 2", Hitch Ball Hole Size: 1", Length: 10", Drop: 5-1/4", Rise: 4", Capacity: 500 TW /5000 GTW, Finish: Metal Shield, Pkg Qty: 1 ---- 1. 海外直輸入品となりますので、新品であっても、パッケージに多少のダメージがある場合もございますが、商品本体には問題ございませんのでご安心ください。2. 日本国内でのメーカーによる製品保証等は適用されません。3. パッケージや、説明書等は、英語表記となります。