Instead of sweeping changes, the Air Force has made subtle refinements to its guidance on how airmen should wear their uniforms.

Published Thursday, the "Interim Change 4" section of Air Force Instruction 36-2903 makes permanent changes enacted in August that specify which hairstyles are allowed for female airmen, said Master Sgt. Cortney Teasley, manager of Air Force Uniform Policy & Programs.

The Air Force guidance memo issued in August about female hairstyles had an expiration date, so the Air Force needed to make the female grooming standards permanent policy, Teasley explained.

Under the hairstyle changes, female airmen are allowed to have micro-braids and cornrows as long as they are a "natural looking color" similar to the airman's hair color and "within reasonable limits" – not extreme, excessive or faddish, according to the guidance memo from August.

The memo also go into detail about how female airmen can wear braids.

"A braid is three or more portions/strands of interwoven hair. When worn, multiple braids shall be of uniform dimension, small in diameter (approx ¼ inches), show no more than ¼ inch of scalp between the braids and must be tightly interwoven to present a neat, professional and well-groomed appearance," the memo says. "Braids must continue to the end of the hair in one direction, in a straight line, and may be worn loose or a secured style within hair standards."

The August memo also made clear that female airmen are prohibited from wearing certain hairstyles.

"Dreadlocks, (defined as portions of hair that have been intentionally or unintentionally fused together to form a loc or locs), shaved head, flat-tops and military high-and-tight cuts are not authorized hairstyles for female airmen," the memo says.

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While the Air Force is not making new changes to how airmen can wear their hair, the service is modifying how airmen keep their heads warm.

The latest uniform guidance says that airmen no longer have to fold their sage green or black watch caps, Teasley said.

"When they folded it, it didn't actually cover their ears," Teasley explained. "So we gave that as optional, just as long as it fits properly."

With the new uniform guidance's publications, all airmen are allowed to wear fitness trackers, such as Fit Bits, while in uniform, Teasley said. The devices track how far airmen walk or run.

Another change allows security forces and fire protection airmen to wear their badge on their sage green fleece, he said.

Airmen in the Air National Guard and Reserve can now wear their specifically designed morale T-shirts under their uniform of flight suits on Friday, Saturday or Sunday instead of just Friday, Teasley said.

Guard and Reserve airmen had complained that they were unable to wear their morale shirts, which have their unit's emblem on them, because they usually drill on weekends, not Fridays. The latest uniform guidance also allows the emblem to be worn on the back of morale T-shirts, Teasley said.

As part of the latest changes to the service's uniform policy, the Air Force is clarifying that airmen can wear permanent badges on their Airman Battle Uniform, not temporary badges, Teasley said.

The approved badges include graduate patches, such as the Weapons Instructor Graduate patch, said Ruth Ewalt, chief of Air Force Uniform Programs and Policies.

The uniform guidance from January 2014 allowed airmen to wear sister services' badges and qualification badges, but it did not adequately describe all of the badges that airmen can wear, Ewalt said.

"We opened the aperture to say, 'qualification and miscellaneous badges and patches,'" she said. "It cuts down the questions that we were getting from the field – we think it will, anyway."

While Attachment V of AFI 36-2903 gives examples of the qualification badges that airmen can wear, the list is not inclusive, said Ewalt, who added, "There's no way we can list them all."