Mine is called an Urban Compost Tumbler. I think that is the name of the company as well. It holds about 40 gallons. There is an axle and cross rod in the center that disrupt the compost when it is turned over.
For some reason, the partially composted product eventually forms into round balls about the size of baseball. Like GB said, they till up OK. In previous years my product has been too wet on the inside, even though there are drain holes in the bottom. On sunny days, I completely remove the top to allow for evaporation. The source of the moisture is the veggies and green stuff that goes in. I add wheat straw to balance it out.
I keep a second compost bin made from a hoop of hardware cloth. I put stalks, limbs, shredded paper, and larger stuff in it. When I empty out the tumbler, I put the contents of the hoop inside the tumbler.
I tried adding earth worms. They didn't live very long. The tumbling may have killed them but I expect the drastic temperature changes are a problem for earth worms as well. The tumbler is black plastic. The sun heats it and it cools at night.
If you build a tumbler, design it to be high enough off the ground that you can tilt the barrel and rake your compost into a wheel barrow. I have to retrieve my compost from the tumbler because in its horizontal position with the top removed, it is too low to pour the compost into a wheel barrow.