What size bung?

[BadMonk]

To mount a saddle on my 1981 Suzuki GS850GLX, I need to drill two holes in the frame on either side of the battery. Then, I'll drop and weld a couple top hat bungs in the holes to keep the strength/integrity of the frame. My question in what size bung is recommended for a 7/8" tube? I've read where guys used M8 bungs on 7/8 frames but they look big to my inexperienced eye. (The top hats I'm talking about don't run through the frame, just one hole.)

[COLDSTEELE]

TC brothers offers their merchandise in American or Japanese catagory So those in the latter should be the size you need what size is the base of your seat spring it should be close to the I.D of the spring