Best original design & patented by Ader Sporting goods Item #10130 Ader Power Twister Original Dynabender, Extra heavy duty tension is perfect for building your hand, wrist, fore arm, bicep, tricep, and back muscles. Heavy duty high grade music wire 6.5mm. Black grip and spring. 75cm long Easy to carry and workout anywhere. NO shipping to Alaska, Hawaii, and APO/FPO addresses or PO boxes Bend slowly, please hold 5-10 seconds. Protect your arm and bender.