The 870 is a low-profile, mildly posted trainer for high-mileage runners looking for moderate stability on long road runs. The heel fit was not what some testers expected, finding it too wide or too low, so that slippage became a problem. This was especially the case in light of the relative rigidity of the 870’s midsole, which reduced the forefoot flex, causing the rear of the shoe to fall off the heel for some testers. Fortunately, lacing the shoe at the top eyelet reduced the amount of slip. The 870 comes in two different widths.