Sports bras are intended to give support and motion control to women's breasts while exercising or during sports activities. They should fit snugly and should be comfortable. A badly fitting model can be very uncomfortable and hurt your performance.
For a high impact activity like running, you will need more support than for walking.
Various types of fabrics are used to make bras. Some popular blends are 1. Lycra/Spandex
There are several styles available. The racer back provides the most support for larger breasts. Traditional hook closures are popular for front and back closures.
Front closure sports bras are easy to put on and take off.
If you wear bras several times a week, you should replace it in 6-12 months. Otherwise you will have a looser fit and more breast motion.
A bra will last longer if you wash it by hand and hang it to dry.
Prices range from about $15-55. If you are active, a higher quality model will help keep you more comfortable.