The machine alloy, which has a long service for time, you do not need to change it often. Easy to use: You just need to unscrew the cap and the internal plate is pushed to the bottom of the cylinder, separate the machine he-ad from the cylinder, fill the oil into the machine, and then the excess air, and finally push forward. Small in size and easy to carry, you can take it with you to you want to use it. Adopt stainless steel compression spring, has fine elasticity, let you feel comfortable even after long for time use. The oil is out and will not leak when using it, give you a better using .