I bought one of these a couple of years ago from a company called
Homier Distributing Company, Inc. they used to travel around the country and have portable sales. It was pretty light and I didn't give it much hope that it would hold up, but I didn't pay much for it either. Surpisingly, it has held up quite well, and has turned out to be 'THE MOST VALUABLE ATTACHMENT" I've ever owned. On the advice of others here I drilled out the holes in the top hook mounting to accept 1/2" pins to make it easy to adjust.