Bought 2 of the 3kg, and 1 of the 5kg units. Following the advice of others, I binned the shot that comes with the units. I'm tumbling rocks in all of them and have run all three units basically constantly for nine weeks (each) - the seal on the 5kg lasted about five weeks, the supplied replacement is in place now. I've had no problems with the 3kg models and would highly recommend that model (especially for the price), noting that plastic barrels are much louder than rubber ones, so invest in some cheap sound proofing if they're going to run in a garage connected to the house or similar. The 5kg unit has, over the last two days, developed some chips around the opening and is now leaking slurry when in operation (the seal helps, but doesn't fully prevent the leakage). I'm about to throw out the 5kg unit and pick up another couple of 3kg units to replace it.