The Buck Sirus is an assisted opening knife much like the Kershaw SpeedSafe knives designed by Ken Onion. Assisted opening knives differ from truw switchblades in that the knife is not opened purely from the force applied by a spring. Instead a cam opens the knife the rest of the way after it has been opened manually a portion of the travel. This is an important legal distinction, but a hardly noticable function one.

The Buck Sirus is available in 420HC and ATS34 steel with a hollow grind and a false edge (or swedge).  The Buck Sirus is also the full sized model in the line with a medium and small size below it.  The Buck Sirus uses a liner lock which is very sturdy and solid in the example I have used.

The safety on the Buck assisted opening knives is in a good place. It is right by the flipper (when the knife is closed), so it is easier to turn on and off than the often out-of-place safeties on other assisted opening knives. The downside is that the safety flops around when not engaged, so you essentially have to secure it after closing the knife. With some other safeties you have the option of never using it at all. And with assisted opening knives it is fairly difficult to open the knife accidently (such as when in your pocket), since the angle required to open it has to be just so. One could argue that such knives need no safety at all.

The Buck assisted opening knives are a great alternative to the Kershaw (and SOG) competitors. It is all a matter of which design you like the most (in terms of visuals and comfort).