I bought a few of these this year. I suppose it was obvious from the name, but I didn't get it until I got the documentation with the product. Here I was thinking it had to do with underwear but it's "Bee Brief Case"! They are thin (four frames and plastic instead of wood) and they have handles so they are very easy to carry two in each hand. Unfortunately, it only comes in deeps, but they are still useful to me. I can put a frame of brood with a queen on it and three empty frames to take a queen to another yard. I can put a four frame nuc in it to take to another yard. When you are moving several of these they are easy to carry three or four at a time (with mediums) as they are usually half brood (which is light) and half stores (which is heavy) so four of them is still usually only about 50 pounds or so. I'm not currently using them for splits as they are deeps and I'm using mediums, but they are nice for transporting and moving things, and with a 2" piece of styrofoam in the bottom might even work well for a medium depth split (there doesn't seem to be any real space between the bottom of the frames and the bottom of the nuc so this leaves a fairly normal 1" space). They are expensive, but not that much more than wood and they are MUCH more convenient to move around and especially much more convenient to stack up and not have ventilation issues. They also make a great toolbox to replace that five gallon bucket that is full of odds and ends. These are easier to carry and you can dump out the tools and use it to collect a small swarm if you need to. I started using them a lot for hauling things like queen cells and such around. They are so easy to pick up and carry!
Now if they only came in mediums...