The 3" version of our Massive Droner comes with a "standard sized" (20mm wide x 220mm) long velcro strap. This strap fits a 850mah 4s lipo onto the Droner well and this is the suggested lipo when coupled to our suggest powertrain of 1407 - 1507 motors. We realize some pilots may not want to run such a monster setup on such a small craft. If you are more interested in running smaller lighter motors and a smaller lipo you will need a smaller velcro strap which is available HERE