Smalls are the bindings we use for our kids when they've outgrown the GROM series but aren't quite ready for the men's & women's bindings yet. They have all the features of the bigger models - capstrap, sick strap, decent highback, amazing baseplate - but are done in sizes appropriate for younger riders. The CHX Snowboard club all ride these.
Grom bindings are the first-step bindings that belong on Choppers, Chicklets, Riglet Boards and After School Specials. As the smallest bindings Burton make they're lightweight, easy to use and will last you for years.