I ordered the T45 from Electric Jet Factory in Arizona. www.ejf.com. I have no idea what retracts they put into the model. They are a large HET dealer also and told mel the next bird to get is the soon to be released HET 90mm F18 with a 55" wing span. Should be out in a couple of months. Thanks for the info on the 4100 battery I'll find a 20c pack. I can not believe the workmanship on these small little jets. Amazing.