B Bosch
Experimental 13g 4-5 inch utility frame . 9--12mm motor mounts, 20, 26, or 30.5mm stack
Ultralight 4-5 inch minimal utility frame. Mount spacing of 16, 20, 26, 30.5, and 40 mm. M3 and M2 holes. 9mm motor mounts. Extra holes for camera, GPS, power connector, etc. About 12 grams