coilover locking rings

Stupid question but the googles let me down - are coilover locking rings universal in size? I ask because I've been trying to install a used set of JIC Cross Competition coilovers on my M3 and realized about half way through that the seller failed to include the locking rings for the height adjustment on the front struts. I've called JIC but they're not much help at this point and I want to get this done. I see other manufacturers selling locking rings separately, is there any chance I can just pick up two and use them on my coilovers?

I'd assume they're not, though you probably only need to know the thread pitch and diameter of the strut housing (if I'm accurately picturing what you're describing). With those measurements, you should be able to find something that fits.

Have you called whomever you bought the coil-overs from?

Assuming you have the seats, but not extra rings to lock them, I wouldn't worry. I know many people who just use a wrap of duct tape under the seat. It keeps them from turning loose and you don't get your seats siezed to the sleeve. I usually stick the duct tape to a tshirt once first to reduce the stickyness. It makes it much easier to adjust them.

I don't think my Ground Controls have locking rings.

Here's a pic of what I'm talking about:

I'm missing the lower red locking ring. These adjust height by means of the lower strut body being screwed higher or lower on the threaded upper portion (which is locked into the strut cartridge) with the springs being separately adjusted for preload. Without that lower locking ring the height will not be locked in, and JIC told me that it'd be possible for turning the wheel back and forth to change the ride height, which is not a good thing. I'll have to get some measurements tonight and probably just order some other manufacturers' replacements to see if anything fits. I emailed the guy I bought them from but he hasn't responded yet, and JIC North America hasn't gotten back to me either (I both emailed and called them). Not great for a company trying to rebuild a reputation after their original Japanese company earned a bad one for customer service.

IF you want to keep the spring seat from moving down just put a hose clamp aroung the strut housing just below the seat. Done & Cheap too!

I have also just drilled the seat and installed a small internal allen set screw to lock the seat and keep it from turning.