Swiss made Gas Mask filters work with any 40MM thread such as Israeli, Russian, British, or German gas masks.   These filters are sealed in a hard rugged plastic case that you need to cut open open around the seal.  They are Authentic Genuine Swiss Army in unused like new condition but may show scratches on the outsides.  Sold only as novelty item and there are no markings with the original manufacture date. 

Features & Specs of the Swiss Military Gas Mask filter

• Fits any 40mm thread used by Nato and others
• Sealed in a plastic container case
• 1 Filter per order