I don't have one of these, but it is very likely that the fatter "head" portion is threaded onto the body. The Chinese have a nasty habit of putting a little epoxy in the threads to make it challenging to open the laser. If the laser is still working fine, you might want to leave it be. If it is broken and you are needing to replace the driver or diode, you'll probably need to wrap some rubber sheet or leather around the laser body and secure it in a bench vise. Then, wrap some leather or rubber around the head and try to visegrip it loose. The rubber or leather are to protect the laser from being marked by the vise and visegrips. You may be able to get the head off if you are lucky, without marking the host.