The SR 90 is an ultralight frame for converting whoops to open prop 2 inch builds. In particular, the Gemfan 2015 biblade props are highly recommended. The frame is kept at 1.5mm so that you can use the regular motor mount screws and not have to go hunting for longer screws. To keep vibrations and noise in check, the arms are kept relatively wide and short to push any resonance into higher frequencies where it can be handled by the filtering

Frame: 90 mm MTM, 1.5 mm thick

FC: 25.5 x 25.5 AIO whoop orientation 

Motor: 1.4 mm on 6.6 mm diameter

Props: 2 inch

Canopy: whoop

Weight (approximate): 2.4 gm