Rappy wrote an answer about Rab Latok Mid Gaiter on April 24, 2012
be careful: low, mid, and tall refer to the height of the gaiter. Small, medium, and large refer to the width and how well it will fit around your calf.
Generally if you hike year round, small will not work. Runners prefer small. The tall gaiters are preferred by people in snow, from snow shoers to cross country to hiking.