Bren MKII or MK I shoulder lock screw. It holds the locking shoulder in the receiver (the piece the bolt rests against). This screw is destoryed in the demill process and is not included in the parts kit. $20 each shipped to you, insurance extra. I accept money orders, cashiers checks, personal, and pay pal. I will hold item until money order, cashiers check, and personal checks clear. E-mail me