Hi my dear Martha
801 dont need adapter to work
510 dont need adapter to work
901 needs one of the small 2 retheaters to work. The second one is a spare.
If you want to put an 801 atomizer, you push the center pin until it comes to same level with the connector's
threads
If you want to put an 510 atomizer, you push the center pin until it goes a little deeper inside the connector's
threads
If you want to put an 901 atomizer or cartomizer, you put the rethreater on the connector.
Dont forget to put the atomizer first and then you screw the telescope until it stops. Dont screw the telescope hard, just stop when you feel a small resistance. Then screw it a very little more, about 1/16 turn