I need one as the gun I bought has a threaded barrel. Are the threads a common size? Before I order one.Is there anything I need to know other than barrel outside diameter?

you need to know the thread pitch. 5/8-24 is pretty common but you will want to double check

is there anyway to check that without "buying it and trying it"
ive seen 2 sizes
1/2-28
5/8-24

get a ruler, and count the # of threads in 1/4 of an inch. multiply by 4. - this is your tpi.
use ruler, measure dia;
done

That is what I was looking for .Thanks

For the most part AR-15s use the 1/2×28 thread pitch and 5/8×24 is the most common thread for 7.62mm/.308 weapons... What type of gun did you buy? AR Platform/Bolt Action/Pistol?

This^^^^

get to plano or close? I have a 5/8x24 protector from my 300bo that you could try.

It is a 552 speedmaster.
R U Sharp thanks for the offer but that is a little out of route.

It being a 22 caliber it is most likely 1/2x28

Like was mentioned, if its on .22 long rifle, its probably 1/2x28 and you can buy thread protectors on line or at most gun shows fairly cheap. If you are unsure about the thread pitch, most smiths can measure it fairly easy and let you know.

You can probably go to a hardware store and get one nut of each thread and try it out on your barrel if measuring makes you nervous.

I have one ordered. We will see if it works thanks for the help.

Sorry I missed this...Harrells Precision has thread protectors cheap. They do require boring and timed to a barrel by a gunsmith but the protectors themselves are cheap.

Good luck and I'm sure it will work out.