OEM Numbers: 424450--OPEL,424452--OPEL,424474--OPEL,13379180--VAUXHALL,13409032--VAUXHALL,13379178--VAUXHALL. All ROC springs are subject to shot peening after coiling, a process which bombards each spring with millions of tiny steel balls to introduce a positive residual stress in the spring; improving fatigue strength and preventing premature breakage.
