This is a small adapter that lets you use larger 1s lipo batteries (550 mah etc) in slots built for smaller 1s (200-250). I built it for use on my brushless UR65 but it should work fine on any brushless 1s quad. I don't recommend it for brushed as the extra weight of the battery is too much.
Amazon Basics PLA
Print vertical with small supports on the bottom of the larger cavity.