The Shield Arms steel magazine catch is designed for optimal performance with Shield Arms S15 magazines. Although it is compatible with plastic OEM magazines, prolonged use may cause accelerated wear on them, and they might not drop freely. Shield Arms advises against using their steel mag catch with plastic OEM magazines, recommending a steel-on-steel or plastic-on-plastic pairing. Note that first-generation aluminum mag catches may not function with Gen 2 S15 magazines, and Shield Arms suggests upgrading to one of their steel mag catch options in such cases.