13x6 prop... motor was broken in when I bought it... and 3 flights after break in... I have a TACH... I leaned it to 9500 RPM but still in the air it was useless... sounded like it was gobbling fuel with loads of smoke... I am now 3 turns out on HSN and 2.5 on LSN... hopefully it will be better tomorrow... OS F plug I am using currently...