i need advice on what kind of chain i need to buy to replace my old one which has now snapped twice in as many months so needs replacing. I know i need an especially toughend chain designed especially for E-Bikes and as a moutain biker its especially nessary so this is my first time. My bike uses a Bosch motor with a derailier gear changer. the problem is they seem to come in narrow medium or large widths so this is were i need advice and if you can put me onto a link were to buy it from. cheers