stock exhaust size?

[euroZ06]

Hi,

I'm shopping for electrical cutouts, and I measured my exhaust at 7.5 inches circumference, and using calculator online I come out to 2.38 inch diameter. The cutouts for sale a re 2.25 or 2.5. Which ones do I buy?

these are the cutouts i'm looking at:

https://www.amazon.com/ENERGY-Exhaust-Cutout-Remote-Valve/dp/B01N42NJ0G/ref=pd_sbs_263_1?_encoding=UTF8&pd_rd_i=B01N42NJ0G&pd_rd_r=KTS00KDF58ZB7NZ2QG7P&pd_rd_w=P0lFn&pd_rd_wg=xOr15&psc=1&refRID=KTS00KDF58ZB7NZ2QG7P

[Nacho-RT74]

originally all are 2.25 up to the end, BUT HP cars got 2.5 up to the muffler then 2.25 from there to the end

About how to measure it? there are several rules to the diameter measurement according to the use and design of the pipe... liquids, gases and stuff. Some are ID, some other are OD some other are nominal... can't talk about that

[euroZ06]

originally all are 2.25 up to the end, BUT HP cars got 2.5 up to the muffler then 2.25 from there to the end

About how to measure it? there are several rules to the diameter measurement according to the use and design of the pipe... liquids, gases and stuff. Some are ID, some other are OD some other are nominal... can't talk about that

I measured at 7.5 before the muffler.

So should I order the 2.25 then?