i bought a formula fastech last year and first run out the flex shaft was slipping like crazy when i tried to get in on plain i think its the collet nut. just in case i bought a new flex shaft as well but i have yet to get a coupler as the stock one seems very poor quality.http://www.offshoreelectrics.com/pro...d=aero-couplerwould this fit on the dynamite .15 and im not sure of the flex shaft size if anyone knows that would be greatly appreciated thanks.