To the OP. Your initial post did not contain very much relevant information. It is always more useful when asking for help to give some pertinent details. For example, do you have a G&G Combat Machine M4 or are you looking at buy a JBBG SpazMonkey - this will help forum members identify a particular make/model which they may have experience of. It is like asking for advice about new alloy wheels on your car; what make, model, year, wheel size, so that people can properly answer the question.
As has been stated, most guns have a thread either CCW or CW so looking at the thread would help determine if A, you have one, and B, which type.