Power Twister Original Ader Dynabender Super Heavy Duty #10150 Double Spring Ader Power Twister Original Dynabender Heavy tension- perfect for building your hand, wrist, fore arm, bicep, tricep, and back muscle. Heavy duty high grade music wire 6.2mm double spring, black grip & spring w/ patented safety wire Easy to carry and workout anywhere. Best original design & patented by Ader Sporting goods Item #10150 NO shipping to Alaska, Hawaii, and APO/FPO addresses or PO Boxes