I use this pod on a mat (it's hard to run outside in the place where I live) and the first results are a bit surprising. Indeed, the distance given by the carpet was significantly different from that given by the couple shows / sensor. This gap increases even if we slowly vary the running speed. It is therefore imperative to calibrate the (ideally on a tour of athletic track before using. Once this is done, it is quite reliable and identical in size to the Nike sensor will fit nicely in a lot of sole models. This was not the case with my pair of Brooks but the support provided lace allows to hang the shoe without problems. A good product for running on carpets or without GPS.
