Call the CBSA, explain your situation and the letter and ask for clarification. Be cooperative and polite and reiterate that it's just a body kit that'll only fit on an airsoft gun. This is my recommendation anyways. Usually they expect a letter explaining yourself.
ďREALITY IS LIKE A STONE. TO MANY ITíS HARD AND COLD, THEY CANíT HUG IT OR EAT IT, IT ONLY FRUSTERATES THEM AND DOESNíT DO THEM MUCH GOOD. TO OTHERS ITíS STRONG AND DEPENDABLE, YOU CAN BUILD WITH IT, BUILD UPON IT, OR WORK WITH IT, ALSO USE IT TO SMASH PEOPLE IN THE FACE.Ē