*PS: Please note: installing parts / assemble /fitting airsoft gun will need intermediate knowledge; for expert or airsoft gunsmith. Please refer to your airsoft gunsmith for proper installation / fitting. Fitting may be needed as the condition of each airsoft gun might be different. Regular maintenance is needed for all airsoft guns in order to keep it in good working condition and reduce wear out issue on parts.
The best replacement pin set which made from stainless steel 303 in tight tolerance. Increase the durability and reduce friction.
For installing the main pin on the frame (the biggest pin). It should able to get in almost half of it easily. Do not punch in the pin if you find it stuck at the beginning. Try the other end of the pin or try to install of the other side of the frame. Damage would caused to the frame / trigger if install on the wrong side.