Master Airscrew props are SHARP! I use wood for the safety factor, they break instead of cutting, at least in my considerable experience with props/fingers/knuckles! I cut two fingers to the bone starting a .61 Super Tiger once. (Yes I learned my lesson.) The tips of APC props can be a bit sharp too. Always sand off the flash before you balance Master Airscrew props. Yes, I still use them on the "Company Trainer", 'cause they are less expensive!

Jetts