. When looking for strength and durability on that next big rigging job, look no further than our array of HSI Wire Rope Slings.•RUGGED FLEXIBILITY – A 6 x 37 IWRC (Independent Wire Rope Core) classification offers large outer wires that provide a balance between fatigue and wear resistance. HSI slings are assembled in an ISO 9001:2015 certified facility where quality, safety and efficiency are priority.