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In Airsoft terms, a defence buying Realistic Imitation Firearms (RIF) is essentially a way of proving that you have a valid reason for purchase. This is typically to stop Realistic Looking weapons getting into the hands of people who want to use them for reasons other than their intended reason.
In 2006 UKARA was formed in response to the 'Violent Crime Reduction' Act (VCRA), which specified that to purchase a realistic looking firearm the Individual must have a reason, or defence, for purchasing it. If you have a valid defence you can purchase a Realistic Airsoft Rifle, if not the weapon must be two toned.
Two tone means the weapon's primary colour must be a non Military colour, such as Red, Green, Blue.
The purchaser must also be over 18 years of age.