We've added several new colors in size 20 long-prong and size 14 KAM plastic snaps, so if you've been waiting for a specific color, we might have it in stock now.
By definition, long prong refers only to caps (the only pieces with a prong). Sockets and studs are the same regardless of the length of the caps.
Standard size 20 cap prongs are 5.6mm in length and are sufficient for most projects, including most diapers. Long size 20 cap prongs are 6.2mm in length and should only be used on very thick material, such as chinese prefold diapers. If you attempt to use caps which are too long for your project, then your snaps won't close properly.