Last but not least, on their site you will see some things which are illegal to own and/or use in some countries. They sell cell phone signal blockers, butterfly (gravity) knives, and brass knuckles which they advertise as "rib breakers"... all of which are illegal to import into the US, but people have mentioned getting them anyways... just a friendly warning for the tempted. These things are not illegal in Hon Kong.
I think the only type of knife that is illegal across the US is automatic/switchblade type knives (see Federal Switchblade Act). Butterfly & gravity knives, which are actually very different tools, vary per state law, same with brass knuckles. Automatic knives were actually banned shortly after West Side Story was released, beaurocrats (idiots) believed the movie was a real depiction of gang life and banned switchblades.
I did some research on auto knives in the past, if you are an EMT/Paramedic, Police Office, Firefighter, or in the armed forces, you can own an automatic knife; most companies, such as Benchmade, require that you provide some kind of paperwork proving your profession.
I know for a fact that gravity knives are legal where I live, I'm not sure about butterfly knives, though. Some of the nicest gravity knives, which are pretty hard to find are the German WWII Airborne gravity knives. You can still find them (sometimes) at gun or militaria shows.
For more information about what is legal/illegal in your area, check out: Knife Laws - Is A Particular Knife Legal in My State?
Honestly, if you are getting into knife collecting, don't bother picking up any Hong Kong junk!
Sorry to go way off-topic, I just like to make sure people know the facts.