the 510 is the best iv tried so far' i always have a fresh battery ready to go. i have 3 batteries and a pcc and a usb so im al set. I retired my 901 long ago because the attys died so quickly, the 801 I dont use either because the cartridge material needed to be pilled up all the time. The mini pipe is ok but not enough vapor i dont use it much. this seemsto be themost durable and great throat hit tons of vapor but you really do need several batteries and a pcc I dont want to spend the money on a screwdriver just yet but that may be my next purchase. i am as addicted to the equipment as I am to the nicotine