How do you know what size to get?
tubbs has a chart that you use according to your weight, I weigh 175 lbs so I use a 25 inch, check out tubbs web site
The size is based on the combination of your body weight and gear.
8" x 21" 75 - 140 lbs
8" x 25" 120 - 180 lbs
9" x 30" 160 - 220 lbs
10" x 36" Over 200 lbs
I weigh 220, and I use the 30 inch models, and they work well for me.
Your weight is the primary factor for shoe size but the snow conditions you encounter also matter a great deal. My smaller size are great for speed on packed trails and fresh snow less than a foot deep. The larger shoe works much better for trailblazing through deeper snow so you don't sink in. I'm short in stature so I prefer the smaller shoe size.
Size generally depends on weight. The larger the size the more weight you can carry. Google "how to choose snowshoes". The REI site has some very helplful information.
I went to the Tubbs website and they have a really helpful sizing chart - it'll ask for intended use (rugged, trail hiking, etc.) and the person's weight with gear. Then it'll recommend the size of snowshoe. Hope this helps!