I have a mkIII and crashed it two months ago due to wrong kind of rubberbands. I bought these at officemax(my bad) and of course they weren't fuel proof or uv protected[:@]!!! what a dumbass I was for buying them! So I orded the relacement parts for the fuselodge and tail set for about 100 bux then I made sure that I bought higher quality bands!!! Thank God for saving my engine and electronics. The engine went into a mud mound witch happend to save the motor I just ran the engine today and it was very smooth this happens to be a .91 fourstroke for the mkIII it could be a little over powered but wanted quicker and shorter take offs so far I quite like it.[8D]