Every two stroke motor I have built has circlips in them, fun little devils aren't they.even more fun when you drop one down in the crankcase . the tool to install them are great but I just use a screw driver, been doing it since I was 12 when I had to replace a piston in my old Moto-Ski,Snowmobile for you warm weather guys.
To remove them just use a pic, most pistons have a notch where you can get behind the circlip and pop it out, wear saftey glasses when doing this or you'll shoot your eye out!!!!