Protech Dark Angel OTF Out the Front automatic knife. The Protech Dark Angel is Protech knives first full size OTF automatic out front opening knife. The prototypes were done in stainless steel in limited numbers. The production run of the Protech Dark Angel OTF knife will be housed in 6061-T6 alluminum and feature a safety. The Dark Angel is sure to be a hit with protechs growing fans. This beautiful fully automatic auto out, auto retract knife locks up tight and is overall open length 8.85 . It weighs in at a sturdy 7.3 ounces with a full blade length of 3 3/4". Handle thickness on this solid stainless steel body is .45". This is a REAL BEAUTY!