Moustache has developed an adapter that allows 500 or even 400 watt batteries to fit into the 625 bracket. I'll just quote from the Moustache page: "The Bosch PowerTube batteries with energy contents of 400 Wh, 500 Wh and 625 Wh are not the same length. To ensure compatibility with each battery, we have developed a Moustache adapter so that you can easily switch between the different battery sizes! With this adapter, you can easily switch between different sized batteries of the same type (horizontal or vertical) and swap, for example, a 500 Wh battery for a 625 Wh battery. So all our new PowerTube frames are compatible with 400, 500 or 625 Wh batteries." https://moustachebikes.com/wp-content/uploads/2019/08/moustache-2019-jrmie-reuiller-4347-1900x1266.jpg