Starter motor bolt size (Intermediate Serp RV8)

[dnb]

I got my starter motor fixed, and now need it put it back on the car.
The old cap screws are looking a bit tired, so I want to replace them, but I can't find my imperial thread gauge anywhere...

What size are they please?

Thanks.

[dnb]

Found it... Why do thread gauges hide from me like chuck keys?

Looks like the bolts are 3/8 UNC.