The main problem with hawkpen design that most of the other pens are based off is the spring that connects to the swashplate. the hawk spring is quite small and brittle apparantly as a lot of these breaK. ive replaced the spring of both of my hawkpens and they run much better now. im not sure of the quality or durability of the clone machines, i did buy a ez filter v2 as a backup which works pretty well though not as powerful but when i tried to open it it seemed a little harder to pry open so i havent inpected it yet. i think they glued it together