"It is an M2x22mm
This one is 25mm long...
http://www.rcfastener.com/0.40x25-12.9-socket-screw-alloy-plain-p-1...
This one is 20 mm long...
http://www.mrmetric.com/metric-fasteners/metric-socket-head-cap-scr..."

"Paint it white?"

"I like the idea but it seems that the prop would lag behind it's theoretical ideal position, causing the disk size to decrease, especially under a load. This may be completely unfounded, just a hunch. The slow-mo guys could clear this up.... Maybe…"

"Just calibrate the ESCs. I've had the same problem several times. Just follow the directions in the video (Jimmy Oliver sent you a link). Your problem should go away. Just remember how to do it because it may happen again when you least expect it."

"Ok, how about an "it's landed" switch that will let the iris know, before it does, that it is in fact on the ground?
ps... I did get mine back in the air today :[)"

"Maybe this is the answer! Turn the legs into handles...."

"A switch to stop the motors seems to me to be a no brainer. I had a RTL that cost four blades possibly due to a last minute gps adjustment. In RTL, I didn't have control of the throttle. In my first prop replacement incident, I let the iris+ land…"