Recreational or 'sport' boots are roomier and warmer, while race boots are stiffer, narrower, and often feature carbon instead of plastic soles. Almost all have a quick-lace system, zip-up lace cover, and hook-and-loop or ratcheting ankle strap. Some have an adjustable heel strap. 'Combi' models have a removable cuff so you can use them for skate and classic skiing.
SNS Pilot boots, which feature two bars, or 'axles,' and a full-length depression in the sole that interfaces with a ridge on SNS bindings, work with Pilot, Propulse, most Profil bindings, and the new SNS Universal binding. Single-axle SNS Profil boots work only with Profil bindings and the Universal binding. NNN/NIS boots only with NNN/NIS bindings.