I wouldn't get one unless you really know how to use it, & they aren't really necessary, you can see the lumps of eggs through to the mommas belly.
Breeeders will use them to watch follicle development. They can put a male with more females this way since they dont wear them out by putting a male with a female when shes not ready.
1.1 Het Albino Ball 1.0 Spider
1.0 Mojave Ball 0.1 Pinstripe
0.1 Honey Bee 0.2 Normal
1.0 Caramel 0.1 Mojave het Caramel