I have several packs of the old 190 screw treesharks,, when I originally got these they wobbled bad right out of the pack,, I called the guy and he took them back and exchanged them all for ones he double checked and they spun perfect and fly perfect.
sharpening,, I bought a few of the wheelie sharpeners and they didn't work good for me,, seemed like they kept taking material off and the edge was sharp but not sharp enough,,, So I got the simmons steel master with the ceramic rods and now I can shave with them..