How well do Galaxy armbands fit?

First and foremost, you need to make sure your Galaxy armband is comfortable. Most are adjustable and designed to fit both men and women, although many warn that fitting is restricted for very large biceps. Piping on the outer edges provides more comfort when wearing the armband for long periods.

What beneficial design aspects are there?

When hitting the gym, cycling or running, you're going to get hot and sticky, so choose an armband with perforations to make it breathable. A sweat-proof design protects your phone from moisture that may accumulate between the band and your skin. When exercising outside in bad weather, a waterproof design is also a good idea. A reflective strip enhances visibility in dim lighting and adds a safety aspect to the design.

Are there other features to consider?

A transparent cover allows you to see your phone's screen while exercising. If your gym gear doesn't have pockets, invest in a Galaxy armband that has a small pocket especially for your gym locker or house key. Some armbands fit different devices so you and other members of your household can share one. Note that some designs require you to remove your phone's hard case.