Long caps have 6.2mm prongs, compared to 5.2mm standard caps. Long caps should only be used on very thick material, such as prefold diapers. If you attempt to use caps which are too long for your material, then your snaps won't close properly. Read more.
Prong length refers only to the cap piece. The same #20 sockets and studs can be used with all lengths of #20 caps.
Offered in limited quantities, this bundle is a great way to have a few long snaps on hand in a multitude of colors. Each bundle includes 20 colors, with 10 sets in each color. Available here while supplies last.