Harbinger Power Amp XXX FlexFast Cable resistance tubes come with exclusive FlexFast handles which secure comfortably around wrist and hand, and offer ergonomic cable connector with multi-position grip. Heavy duty door jamb attachment increases exercise options. Harbinger Power Amp XXX FlexFast Cables are constructed with lightweight, portable latex-free tubing and come in different resistance options ranging from 10 pounds to 40 pounds.