An item with an integral porous or perforated plate, or with slits on the inside of a double wall.
NSN 6620-01-184-7384
NSN 6130-01-472-1427
NSN 5920-01-550-1810
NSN 5930-01-659-1942
NSN 5925-00-007-3962
NSN 6320-00-036-3688
NSN 6610-00-239-8613
NSN 6130-01-094-1502
NSN 6610-01-394-4944
NSN 4140-00-269-5795
NSN 2925-01-368-1333
NSN 6145-00-851-0898