Powerstep Slim Tech at Robert Frost Fine Footwear and Frostshoes.com. Slim Tech provides the versatility of a 3/4 length support with a slimmer, thinner approach that fits most casual, slip-on and dress shoes. In independent research with over 150 product trials, Slim Tech was proven to have advantages versus its leading competitor in overall product preference, pain relief, fit, and comfort! The Powerstep Slim Tech features: A prescription-like polypropylene support, calibrated with flexibility for comfort. Stabilizing heel cup and neutral (flat) platforms at the heel and midfoot. Unique Hypercel cushioned insole. Special antibacterial fabric to reduce slippage and heat, keeping feet drier! Sizes are featured in letter form and convert as follows: a: 4-4.5 Mens and 6-6.5 Womens, A: 5-6.5M and 7-8.5W, B: 7-8.5M and 9-10.5W and so on. Powerstep Slim Tech is available at Robert Frost Fine Footwear and Frostshoes.com.