These are 810 size drip tips. They have diameters around 12.5mm and sometimes have o-rings. Usually, 810 drip tips for rebuildable atomisers [RDA, RTA, RDTA, etc.] do not have o-rings, and non-rebuildables do, but always check your atomiser.

If the atty has an o-ring in the top cap, then it needs a drip tip without o-rings and vice versa. If you need 510 drip tips, head over here.