This battery is the best upgrade I have made to my TK1 folding. The increase in torque is very noticeable, especially when climbing steep roads and trails. I noow use the 20ah as my main battery, and the 14.5ah as my spare...enabling me to double the distance I travel. That opens up more possibilities! I read other reviews that mentioned various things that needed to be done to use this 20ah battery, but let me assure you that all I had to do was slide off the original and slide on this one. I don't know what the "loosen screws and this and that" talk was all about. I will warn you that this battery is almost always out of stock, and don't count on hearing from Mooncool if you ask them to email you when it's back in stock. I did that and never heard anything from them. I would check their website everyday until I saw that it was in stock, and ordered immediately. GOOD LUCK TO YOU, IT'S WELL WORTH THE EFFORT!!!
