Thread size? I mainly do auto seat repair. I have used 69 thread for 22 years, I also think that 92 is extreme overkill to sew car seat covers together. There is nothing wrong with using 92 to sew the top stitch, accent and french seams, except the cost of buying 92 thread that is the same color you just used to sew the cover together. I even use 69 for the top stitch, with no complaints. This week I have to replace all the inserts in the front and rear seats of a Jeep Wrangler, with day glow green vinyl. I had to buy 92 thread because it was the only thread that would match the color of the vinyl, I couldn't find it in 69. But I will only use it for the top stitch. I don't understand why people use 92 thread to sew covers together. I wish I knew.