[AtlUmpSteve]

Not trying to be the ASA apologist, here. The official ASA uniform covers visible garments, not undergarments. And visible undergarments (the collar of an undershirt, for example) are only governed by the color; white under powder blue shirt, navy blue under navy blue shirt.

So, you are free to wear, even in the finals of an ASA National, any added undergarments required; and layers of "Underarmor"-type garments are the best, lightest, etc., anyway; far better than any set of sweaters, jackets, or any other outerwear I have worn. The "cold weather" gear is outstanding.

Beyond that, black or navy blue gloves are generally acceptable. Underarmor also makes a navy blue head covering which is great complement to (and thin enough to) wear under your official ASA hat, and covers your ears from the wind. Those items sold by most major umpire equipment sales companies, if color compatible, are generally acceptable.