USGI Chemical-Biological Mask Facepiece (M40, M42) Second Skin

The US Genuine Issue Chemical-Biological Mask Facepiece (M40, M42) - aka Second Skin or Outer Skin - is in new unissued condition and sealed original packaging.  It comes in two sizes: Small and Medium-Large.

This component of the mask Mask partially or completely encloses the user's face and fits over the base skin of the mask assembly. 

NSN

• Small: 4240-01-413-1540
• Medium-Large: 4240-01-413-1543

Features

• Butyl Rubber Material: Unlike the silicone facepiece of the M40 mask, the second skin is made of thick butyl rubber. This material provides superior resistance to penetration by chemical warfare agents, particularly blister and nerve agents, which can corrode or permeate standard silicone.
• Contamination Protection: Its main purpose is to shield the inner mask from liquid chemical droplets, significantly extending the service life of the respirator and simplifying the decontamination process.
• Snug, Close-Fitting Design: The skin is molded to fit tightly over the outside of the mask's facepiece. It includes small rubber tabs at the forehead and chin areas to secure it firmly and prevent it from slipping.
• Size Versatility: While the small size requires its own specific skin (NSN 4240-01-413-1540), the Medium/Large skin (NSN 4240-01-413-1543) is designed to fit both medium and large facepieces.
• Compatibility: It is fully compatible with the standard M40 and M42 series components, including the voicemitters and filter mounts. It is often issued alongside clear lens outserts and protective hoods to provide a complete seal.