Why 4-Blade? An extra wing on the prop means more thrust if you have powerful enough motors, but sacrafices spin-up time just a bit, having more mass to push around. 

These are 40mm (about 1.57") light weight yellow propellers for micro class drones, made for 1mm motor shafts.

Specification
- Type : Micro Class Multi-Rotor
- Length : 40mm / 1.57"
- Mounting hole : 1mm Motor Shaft
- Included : 2pcs CW and 2pcs CCW in a bag