Libima 20 Pcs Plastic Propeller for Stem Activities 7.1 Inches Fold Resistant Propeller Blades with Rubber Band Hooks for Airplanes and Helicopters from Research Institution, Black

These are just what I was loking for for my rubber band powered models.

We did a STEM challenge making a plane. This didn't go the way I had hoped. We had all the rubber bands and craft sticks to do this. We found that 2 skewers worked great to fit in the holder part. When we did the rubber bands to wind it up most of them had a hard time free spinning and in turn would just not spin. Where the plastic was there were a lot of extra plastic the kept it from spinning correctly. It was like they make them and didn't cut off all the tabs or something. The kids would spin them up and then they wouldn't budge or if they did it wasn't much. We got about half of them to spin with out that extra plastic getting stuck but even those felt like they didn't spin as fast as they should have.

Nice and big for stem activities. They are very durable and easy to use. They are a bit larger than the props that come on the little balsawood airplanes I had as a kid. The hook attaches easily to a wide range of rubber bands.