I use the largest container of liquid clothes detergent at the store with a handle and fill it with water. I haven't weighed it, but you're in really good shape

I use the largest container of liquid clothes detergent at the store with a handle and fill it with water. I haven't weighed it, but you're in really good shape if you can curl it. Great for dumbbell rows and shrugs, though too unwieldy for much else.