If you have a large or heavy machine, Make sure you check the specs on the weight that the shelf will hold, some of these units were originally manufactured to be computer desks and the shelf was meant to hold keyboards, which weigh considerably less than most sewing machines. I looked at one that looked similar to that one and although it was rated to hold 25 pounds, my Kenmore weighs in at 27 pounds, so I went for the Arrow Gidget which was on sale last spring for $100 with free shipping.
Rob