The swivel Omni pulleys (blocks) are hewn from a solid block of high strength aluminum and are engineered with great pride to withstand over 8,000 lbs (36 kN) of tensile force end to end. Sterling Rope Company has also designed sewn products for these pulleys including the 8 mm restraint cord, rated at 4,270 lbs (19 kN) and both ratchets in two colors, and shockabsorbing/restraint cords. These pulleys configured as "set-of-fours" (double blocks) will enable the rescue practitioner greater versatility in a personal mechanical advantage (PMA) for rescue and general rigging.absorber/restraint cords. The set of two blocks are different colors for ease of identification. Turn the set-of-fours one way and you have a 5:1 mechanical advantage. Turn it around and a 4:1 w/change of direction is the result, making this PMA extremely versatile. Also, the progress capture ratchet prusik can be attached at either end (orange to orange, or blue to blue). The progress capture prusiks are laced onto the restraint cord and then formed into a directional prusik hitch (3 on 2), which prevents the inadvertent loss of the prusik once assembled. One quick pin is sold with each set of blocks. Additional pins may be purchased if needed or if one wished to hold a spare in the opposite block. Made in the U.S.A.