These bikes are ones that come as 28mph (L1e) but can be de-restricted to increase speed. The resulting speed is dependent on the bike, the charge on the battery, the terrain, temperature and load (ie rider) but typically they get to high 30s, low to mid 40s mph.
Please note that when doing this, technically the bike has changed from a 50cc equivalent to a 125cc equivalent and hence your licence and insurance need to support that type of bike.
Please also note that there are no guarantees that these bikes will continue to be de-restricted, ie the manufacturer might disable this feature without notice. We sell these bikes in good faith at the time of purchase.