Parker Instrumentation A-Lok Fittings meet the stringent demands of process control, power and instrumentation systems. These dual ferrule fittings provide leak proof connections and are used in chemical, petroleum, power generation, laboratory, and medical device plants. Small Parts Stocks A-Lok Fittings made from Heat Code Traceable 316 Stainless Steel and Brass. They are compatible with all types of stainless steel, copper, and various rigid and semi-rigid plastic tubing. These fittings are not recommended for soft tubing.