Containment Series, This Special Series we started a couple years ago. With this series we start with a base knife and add unique gas mask graphics which are laser engraved into the titanium. Each year we use a different “gas mask” design thereby making each knife more unique. The finish and overall appearance of each knife is also different and unique and made in a very limited number. The RHK Containment Series has always been a very popular RHK offering!