The ACU patrol cap is a visor style, having a circular top crown with a two-piece inner crown lining forming a pocket between lining pieces.

USMC cold weather cap is not a replacement for the currently sustained USMC microfleece hardface cap but would be worn separately from the current cap when increased protection from wet and dry cold weather environments is needed.

The olive drab cotton field cap is a visor style with retractable earlaps lined with wool flannel, and grommets for ventilation. It was designed to be worn with the M-1943 field jacket. It could also be worn under the hood of that jacket and with the steel helmet and liner.

The olive drab pile field cap consists of a wind-resistant, water-repellent, poplin outer shell with a pile lining, a flexible visor, which can be worn up or down, and pile ear flaps with an drawcord closure. It was designed for wear in extreme cold.

The MQ-1 (Model Quartermaster 1) olive drab pile field cap is a modified version of the olive drab pile field cap. The pile lining of the original visor, which caused visual interference and forehead discomfort when the visor was lowered, was eliminated. The MQ-1 cap was adopted as the M-1951 pile field cap.

The M-1951 cotton field cap is a visor style with a circular top crown and retractable earlaps, and is a lightweight windproof item incorporating a very thin layer of insulation only in the earlaps. It was designed for ground troop wear in a range of cold-wet to hot environments.

The M-1951 pile field cap may be worn for both cold-dry and cold-wet conditions. The cap provides the best protection against the elements for weather colder than 0°F.

The M-65 cold weather insulating helmet liner cap is worn alone or as a liner for the helmet assembly. The earflaps are fasten under or over chin, at back of neck, or are folded up around the top with the touch-and-close fasteners crisscrossed in the front.

The hardface micro fleece cap is intended for wear by male and female military personnel of the USMC in mountainous and cold weather environments.It will provide improved wind resistance, durability and water repellency when worn in intermediate to cold weather environments.It will be part of the Mountain/Cold Weather Clothing System and will ultimately replace/phase out the current micro fleece caps.

The hot weather field cap is a baseball-style cap made of olive green shade 106 polyester and rayon gabardine cloth, conforming to MIL-C-41820. It was intended for wear as a component of the hot weather field uniform and the OG-107 utility uniform.

The OG-507 hot weather cap is a baseball-style cap, with a visor and stiffner on the inside front, and was intended for wear as a component of the hot weather field uniform and the OG-507 utility uniform.

The knitted wool watch cap is intended for wear by Naval and Air Force personnel in cold environments.

The patrol cap, formerly called the battle dress uniform (BDU) cap, is a visor style with a circular crown and retractable earlaps, which is the same basic design as the M-1951 cotton field cap. It was intended for wear with the temperate battle dress uniform.

The hot weather patrol cap is a visor style with a circular crown and air vents. It was intended for wear with the hot weather battle dress uniform.

The microfleece cap is intended for wear as multipurpose lightweight head protection.

Commercial item description A-A-50369 covers the requirements for a Cap, Knit (Watch) used by Navy personnel in cold environments.

Commercial item description A-A-55294 covers the requirements for a visor style cap that is intended for wear in hot weather environments by military personnel of the Department of the Army.

Commercial item description A-A-55312 covers the requirements for a visor style cap that is intended for wear in a temperate zone environment by military personnel.

Commercial item description A-A-59453 covers the requirements for a synthetic microfleece cap that is used as multi-purpose lightweight head protection.

Commercial item description A-A-59788 covers the requirements for a visor style patrol cap with inside pocket on crown of cap, intended for wear in all environments by military personnel of the Department of Army.

Military specification MIL-C-10869 covers the M-Q1 (Model Quartermaster 1) pile field cap.

Military specification MIL-C-16472 covers the requirements for a knitted wool watch cap.

Military specification MIL-C-1911 initially covered a cap made from olive drab shade 7 cotton poplin with flannel lined earlap.

Military specification MIL-C-1913 covers a cotton poplin, field cap with wool pile lined earflaps.

Military specification MIL-C-3000 initially covered a cap made of od-7 herringbone twill cloth, and then a cap made of og-107 cotton sateen cloth.

Military specification MIL-C-43225 covers a baseball-style cap made of dyed olive green shade 106 polyester and rayon gabardine cloth.

Military specification MIL-C-43549 covers a fully lined insulating helmet liner cap with adjustable forehead flap.

Military specification MIL-C-43724 initially covered a hot weather field cap made from olive green shade 106 polyester/rayon gabardine cloth, and then a hot weather cap made from olive green shade 507 polyester/cotton durable press material.

Purchase description MC/PD 04-2011 SYSCOM covers the requirements for the U.S. Marine Corps cold weather cap.