The long prong snaps have caps with a longer prong. The other pieces stud/sockets are the same as in standard snaps. Only the caps are different.

Long prong caps are more suitable to apply on very thick layers of fabric.   

Size	Cap Diameter	Standard Prong Length	Long Prong Length
20	12.4 mm	5.6 mm	6.2 mm

Those snaps are sold as full sets :

• 100 studs + 100 sockets + 200 caps