The belly band only covers the 'daddy parts'...not the factory at the back!
They do work...I use them on Murfee when one of the girls is in heat...that's the only time he wants to mark. I use an Always pad inside, they have a gel in the middle that traps the urine and keeps everything dry.
A word of caution for those who use them to prevent breeding though: CHECK THOSE BANDS OFTEN!
Maddie just went through the world's longest heat (we were all miserable and sleepless!) so I kept panties on her and a belly band on Murfee. I noticed a spot of pee in the living room that looked like it was done leg lift style so I checked Murf. From his attempts at mating with Maddie he had scooted the band down and was able to pee outside of the band
and it occurred to me that they could have tied under the right conditions. They never connected during her heat but it sure got my mind racing!