This battery is about 25% larger than our 2.9ah pack. It still is fairly compact, yet if provides almost twice the power capacity. Again, we built this NEW larger box platform specifically around this 5ah pack. Now run your fish finders for longer durations prior to needing a charge. May we suggest you purchase two even for your extended trips? Does not fit within 2.9 amp hour kits - ONLY for use with 5 amp hour systems! Do you have a proper battery charger for your FTF battery? We have a great charger for you on page 2 of our 'Buy Now' page, if you don't already have something suitable.