This is a 3D printed Folland Gnat T.1 for the Xfly Galaxy X3 30mm EDF. The model weighs just 194g with a 4S x 450mAh Tattu pack.
For details see RCGroups thread here:
https://www.rcgroups.com/forums/showthread.php?4717107-Folland-Gnat-for-Xfly-30mm-EDF
70mm and 80mm versions have also been under development.
Tiny Gnat is well under the 250g mark - only 194g ready to fly.
It's a tight fit, but 2 x 4.3g servos fit along with a 6ch rx, 12A esc and HobbyEagle EVO gyro.