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One incredible, discreet true double edge folder! - Extrema Ratio BF4 Contractor Linerlock Folding Knife

by Michael J Perrine, Verified Owner from SC, United States Written on February 9, 2026
Review for Extrema Ratio BF4 Contractor Linerlock Folding Knife
Extrema Ratio BF4 Contractor Linerlock Folding Knife
Extrema Ratio BF4 Contractor Linerlock Folding Knife
As Low As $259.99 Save Up to $17.14
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Michael J Perrine's Review of Extrema Ratio BF4 Contractor Linerlock Folding Knife

I first of all took the all black option for concealment. The double edges are razor sharp as are the matching serrations. The length is an actual length of OVER 4'' blade to truly act as a concealed dagger when presented open. The handling is fast. light but tough and the flipper system is smooth and fast. I really got excited over this as soon as I came across it and really favor it as a back up, out of the way knife. This is a great buy! Go for it! Semper Fi, God Bless! Cujo
Pros:
  • Razor sharp edges
  • Great deep pocket carry
  • Fast flip action
Cons:
  • None
Best Used for:
  • Defense, man or beast
Would Recommend: Yes
Was it helpful to you? Yes | No
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About Michael J Perrine from SC, United States

At 14 I had my first gunfights in woods where we weren't wanted by certain people. After 4 dogs shot and 1 of my dogs was stabbed, I started hunting the poachers and thieves. I drove them away and ended up on the survivalist path. I am a former Marine, Fast Attack Submariner, soldier-unit armourer and M60 machinegunner. I was FBI trained/certified as an L/E Academy Firearms Instructor & former government contractor. When I was first assigned to the FBI instructor class, I had a broken right ankle, which I hid and wrapped in my boot. The instructors identified my injury on the fourth day but allowed me to continue if I could pass, or return later. I finished the next weeks and passed. I developed defensive tactics based on a lifetime of studying and training in multiple martial arts and honed it working in 2 prisons/2 jails and u/c work. I have stopped 2 terrorist events, one domestically and one in W. Germany. A drunk driver caused my TBI disability/aneurism&constant migraines,sadly.