I have the medium, large, and XL protons, and the larges are the most interesting. The XLs are fun but pretty straightforward, the mediums are the best for pinching, but the larges are hard to figure out how to grab them until you put your hand on them. Fun to force a match so you have to pinch a single ball. Fairly rough texture which I usually don't like, but it's good here since the shapes are so round and it's a relief to have that extra friction.