The t-shirt shall have short sleeves, a crew neck collarette that shall finish 3/4 + 1/8 inch wide. The sleeve and bottom shall be hemmed approximately 3/4 inch from edge. All seams shall be overedged or cover stitched. The color shall be Olive Drab.

The mesh cold weather base layer (MCWBL) is similar to flame resistant lightweight cold weather underwear set except the fabrics and design have been modified to improve moisture regulation and thermal performance in an extreme cold weather environment.

The polypropylene undershirt and drawers are new ECWCS development items. The underwear layer next to the skin acts as a moisture wicking layer and serves to draw moisture away from the skin, transferring it to the outer layers.

Lightweight Cold Weather Underwear Set (LWCWUS) was developed to provide a moisture wicking, heat retentive, lightweight garment for moderate conditions not sufficiently cold for the polypropylene underwear.

The undershirt and drawers are designed to be worn next to skin by itself and to transfer moisture from the skin to the outside of the fabric where it spreads rapidly for quicker evaporation.

The shirt and drawers are designed to provide light insulation for use in mild climates as well as a base layer for colder climates, worn next to skin by itself or in conjunction with other levels (level I) for added insulation and to aid in the transfer of moisture.Fabric is slightly different than level I in that it provides extra warmth but still wicks moisture away from the skin to allow for quicker evaporation.

The LEP layer 1 silkweight undershirt and drawers are intended for wear as a moisture wicking layer of the ECWCS.

The LEP layer 2 midweight undershirt and drawers are intended for wear as an insulation layer of the ECWCS.
The M-1950 winter undershirt and drawers serve as inner layer in cold-wet and cold-dry climate.

The M-65 cold weather undershirt and drawers serve as inner layer in cold-wet and cold-dry climate.

The mesh cold weather drawers are part of a base layer set intended for use with the cold weather clothing layering system worn by personnel of the United States Marine Corps.

The mesh cold weather undershirt is part of a base layer set intended for use with the cold weather clothing layering system worn by personnel of the United States Marine Corps.

The mid-weight FR grid fleece underwear is a flame resistant version of the polyester grid fleece underwear.It will provide improved moisture management, insulation and comfort when worn in intermediate to cold weather environments. In addition, it will provide Marines with FR protection when needed. The FR Grid Fleece can be worn as part of the Mountain Cold Weather Clothing System or Flame Resistant Organizational Gear (FROG).

The mid-weight grid fleece underwear is intended for wear by male and female military personnel of the USMC in mountainous and cold weather environments.It will provide improved moisture management, insulation and comfort when worn in intermediate to cold weather environments.It will be part of the Mountain/Cold Weather Clothing System and will replace the current polypropylene underwear set, and fleece pullover.

The FR next-to-skin underwear is a flame resistant version of the polyester silkweight underwear.It will provide improved moisture management and comfort when worn in intermediate to cold weather environments. In addition, it will provide Marines with FR protection when needed. The FR Silkweight Underwear can be worn as part of the Mountain Cold Weather Clothing System or Flame Resistant Organizational Gear (FROG).

The new next-to-skin underwear is intended for wear by male and female military personnel of the USMC in mountainous and cold weather environments.It will provide improved moisture management and comfort when worn in intermediate to cold weather environments.It will be part of the Mountain/Cold Weather Clothing System and will also replace the current lightweight CW underwear set.

The FREE system t-shirt and boxer briefs next-to-skin layer is constructed with a tri-blend of lenzing FR rayon fiber, wool, and nylon. This layer is extremely lightweight and breathable to allow high moisture movement and quick drying.

The FREE system undershirt and drawers base layer is constructed with a lightweight moisture wicking and breathable lycra mesh fabric made with DuPont Nomex fiber. This base layer provides maximum comfort and excellent recovery properties in hot climate, and can be worn under other layers like the mid-weight shirt and drawers for additional protection for cold weather.

In addition to being FR, this shirt has a mock neck design for added protection and also contains an antimicrobial property along with moisture management (wicking) capabilities.