Extra strong bright green Callicrate PRO Loops™, for use with the PRO Bander™, are specially formulated to withstand and maintain the high tension needed for consistent results. The special latex formula is over three times stronger than comparable latex rubber. The formulation and curing of the rubber gives it the elasticity, strength and memory necessary for fail-proof application. The PRO Loop™ uses a self-locking clip - no crimping required. High tech. Built to last. Callicrate tough. For delayed castration (300 lb to full grown).