Look at the Robo website. The design has a cut-out shim that allows you to combine brood frames with the colony. I made one using this design and it works great. No more pouring bees into a hive box after you vac.Bee vacs are mostly used when removing bees from structures. If you vac the bees into the hive, you have no way to install the brood comb you put in frames for the bees. It is best to vac into a different container, frame the comb, and pour the bees over the comb once you get them home.
If your budget is really tight, you can build this one for about $30. It works great. I've done about 35 removals with this type and very little to no bee loss. All the queens made it as well.