There are a variety of retainers and locks available having different degrees of strength and lightness. Selecting retainers begins with getting one that fits the spring. Retainer choice can also significantly affect the installed height, since retainers vary in the amount of "dish" in their profile, which alters their height. If more installed height is needed, specialty locks can be had which raise the retainer's position. Locks also vary from cheap stamped units to heavy-duty machined pieces heat-treated to carry extreme spring loads. Though most standard retainers and locks mate at a 7-degree angle, some aftermarket manufactures like COMP offer extreme-duty 10-degree pieces, drastically reducing the possibility of a lock pulling through a retainer. The 7- or 10-degree locks and retainers must always be used as a set.