I like to use the front loading trays on bookshelves for our homeschool paperwork. They take up less space than the side loaders. These hold plenty of paper and also take clipboards but some pocket folders don't fit well (could be squeezed or angled).
I had changed printer stands with my wife which left me with a narrow space underneath to hold printer photo and scratch paper. I had been fruitlessly searching for trays that would be "front-loading" and fit in a narrow space. Until I found these trays. I bought 4 (2 packets of 2 each) and they fit under my printer PERFECTLY!!! I highly recommend this product!!!