The GT2170 continues with the 2100 series which I find the best type of shoe (stability/cushion) for running. The GT2170 is comfortable for running on the track and on grass/dirt surfaces. The GT2170 replaced Asics trail shoes that caused problems with bilateral calf muscles and problems resolved 1 to 2 weeks after using the GT2170 shoes. I made a mistake in using trail shoes and am glad I purchased the GT2170 shoes.