The SM-90 is a modern gas mask/respirator manufactured by the Swiss company Huber & Suhner for the Swiss military, however other countries such as South Africa and Singapore also use this mask.
Production of the SM-90 started in the early 90's due to Switzerland needing a new protective mask fitting the "modern respirator" description, the SM-90 is an NBC/CBRN/ABC rated mask intended for military use and is made of a very comfortable, soft black rubber, most likely butyl. The mask features a drinking tube, "6 point" mesh head harness, locking head harness buckles (made of metal), an orinasal cup, voice diaphragm and removable tinted/flashbang outserts.
The mask uses the standard NATO compliant 40mm threads which means that almost all filters containing 40mm threads can screw into the inlet of the SM-90. The filter inlet, voice diaphragm, drinking tube and exhale vavle assembly are located in the centre of the mask, as the filter is located in the centre of the mask this means the SM-90 accomodates for both left and right handed shooters, no ajustments need to be made to accomodate either left or right handed shooters.
The lenses are made of a durable scratch resistant material called mineral glass and is definately one of the best materials I've seen being used in the manufacturing of lenses, the tinted outserts are made of hard tinted plastic and unlike the usual US style outerts which feature a rubber lip that fits over the exsisting lenses the SM-90's outserts simply clip over the existing lenses making it far easier to put on and take off.
This mask is exremely comfortable to wear and hardly ever fogs up thanks to the removable orinasal cup, however as with most gas masks it gets quite hot inside the facepiece making it unpleasant to wear after long periods of time. The head straps are easily adjusted and the top four buckles lock into place. Essentially the head harness works similar to that of the Russian skullcap as seen on the GP5, with the exception of the last two straps being ajusted upon donning the mask. Overall the SM-90 is a great mask but is quite challenging to find at a reasonable price.