Comfortable and Protective: Hedley & Bennett The Wake Up & Fight Mask
These Hedley & Bennett The Wake Up & Fight Masks ($36 for three) are no-nonsense masks that don't take up much space (easy to put in your pocket on a walk, for instance). They have a slot to put in a filter, and they're washable. They also have adjustable ear loops, so you can make it as tight or loose as you want. Plus, they donate one for every mask purchased.