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Model 40Reversible handingSized spring (2-5)Identified by number stamped on lid

Model 50HandedSized spring (3-5)Identified by number stamped at fill plugSingle spring tube

Model 70HandedSized spring (3-5)Identified by number stamped at fill plugDual spring tube

Model 150HandedSized spring (3-5)Identified by number stamped at fill plugBackcheck adustment

Model 1220Non handedAdjustable spring tensionIdentified by number stamped at end plug
 

Model 1230Non handedSized spring (3-5)Identified by number stamped at end plugNo backcheck

Model 1240Non handedSized spring (3-5)Identified by number stamped at end plugNo backcheck

Model 1250Non handedSized spring (2-6)Identified by number stamped at end plugBackcheck

Model 1251Non handedSized spring (1-6)Identified by number stamped at end plugBackcheck