PSA Gen II upper receiver barrel extension threads?

[se3388]

I was looking over hand guards for my upcoming PSA 10 build and noticed some ads offer a 16 tpi or an 18 tpi barrel nut, which fits the PSA 10 Gen II upper receiver? Thanks for any info.

 

Steve........

Edited October 9, 2017 by se3388

[Boot_Scraper]

16 TPI and the "low" rail height. 

[se3388]

Thanks, I had already caught on to the low height thing but couldn't find anything about the tpi.

 

Steve............