I didn't guess these numbers, I know them. I've owned and installed over 10 sets of SSAC's myself, along with working with every other style I listed, except ZZP's* & Big Dogs (but I'm also old enough to remember reading their product description many times). SSAC's are 1.625" OD primary tubes (1-5/8"). Zoomer also confirmed this, back when they got popular and he thought he could buy a set to disprove their worth, and couldn't.
*will be installing a ZZP set for a customer next month, only because he didn't ask about options before ordering headers for $900 instead of $350
SSAC's description was some lazy marketing employee's sloppy copy-paste job of PaceSetter specs. I've emailed them asking to revise this number and the other error, since they short-change themselves by not properly saying how they're a 300-grade of stainless, NOT mild steel. Even though they obviously get alot of orders, it seems this description isn't something they're worried about editing.
- Dave