The Service Dress Blue (SDB) uniform consists of a dark navy blue suit coat and trousers (or optional skirt for women) that are nearly black in color, a white shirt, and a black four-in-hand necktie for men or a neck tab for women. The material is generally wool or a wool blend, depending on the vendor. The men's jacket is double-breasted with six gold-colored buttons, and the women's jacket single breasted with a single row of four gold-colored buttons. Rank insignia are gold sleeve stripes for commissioned officers, while rating badges and service stripes are worn on the left sleeve by chief petty officers (CPOs). The prescribed headgear is a white combination cap, although a navy blue garrison cap is optional in some situations when the jacket is not worn, unless stated otherwise by the prescribing authority. Beginning in 2016, the Navy began phasing out the distinct female combination cap and now prescribes a cover similar to the male version for female officers and CPOs; the prior female versions were authorized for wear until October 2018. Commissioned and warrant officers above grade W-2 wear a cap badge of the U.S. shield and eagle in silver upon gold crossed anchors, warrant officers at grade W-1 a pair of crossed anchors, while CPOs wear a single fouled anchor. The combination cover's chinstrap is gold for commissioned and warrant officers, narrower gold for midshipmen and warrant officers 1, and black for CPOs. Females typically wear beltless slacks with the SDB, although since January 2017, belted slacks can be worn as an alternative.