How long is a piece of string. There's a lot of variables.
The more elements, the more stacked yagis, better conditions, better feedline, matching and modification.
As cokebottle highlighted, they're not exactly designed for UHF CB, but they are close enough, so a few simple modifications and they do work
fine. The low band UHF TV antenna (band 4) not the band 5 which are too far out.
It's easy enough to check. Measure the driven element. The closer it is to 32cm wide the better.