If you can get one out, take it to a hardware store that has the free to use thread gauges in the nut and bolt aisle. I know Menards has them for customers to test thread gauge and pitch.
They are M10 x 1.5, and not really all that tight on my 2021 RTL, but do have a locking compound on them. I replaced one with a long stud and coupling nut with about 1/2 of the hex cut down on my lathe, then mounted it (with blue locktite) in place of one with a RAM ball screwed in it. Worked great to mount my GPS.
"Love 'em all.... Let GOD sort 'em out!"
2021 RTL Dark Chalk Metallic with comfort seat
1978 GL1000 w/'75 engine show bike
1976 RD400c