From journalists and cameramen to politicians and security staff, we're all used to seeing people in body armour on our TV's and increasingly on our streets.
A bullet-proof vest should cost you about £260, but will stop a bullet from just about any handgun short of a Magnum - even at close quarters.
They're popular not just with police forces, but increasingly with security firms and even ordinary members of the public.
But unscrupulous dealers are selling second-hand vests online and through surplus shops.
Experts say many are useless, either old and degraded or designed to stop blades not bullets.
46-year-old Philip Harper from Meldreth near Cambridge bought what he thought was a bullet-proof vest.
He died in June last year after being shot in the chest by his friend Ian Catley.
They decided to test the body armour while out shooting on this farmland south of Meldreth.
Mr Harper's mother described him as a "delinquent Ray Mears" who was always up for a challenge.
Catley admitted manslaughter and today was sentenced to seven years at Southwark Crown Court.
Experts say no-one should buy or trust any military equipment bought second-hand or from anything other than a reputable source.
Judge Jeffrey Pegden QC heard that after the shooting Catley took his friend to Melbourn ambulance station where he died.
Catley told police he'd only fired, because his friend wanted him to.