510 Tips
Will fit any 510 tip tank or 510 adapter. The size, 510 represents an insertable (in to the device) diameter of approximately 8.5mm. More o-rings on the insertable portion of the tip means less moisture collection and more stability.
810 Tips
Will fit any 810 tip tank or 810 adapter. The size 810 represents an insertable (in to the device) diameter of approximately 12.5mm. More o-rings on the insertable portion of the tip means less moisture collection and more stability.
Drip Tip Materials & Design
There are a great many options for drip tips, but it's going to come down to choice. Some people like a larger bore, especially if you are old school dripping in to an RDA. Some tips include a mechanism for advanced airflow. Materials range from resin (plastic), stone, glass, metal and more. I personally avoid any material that easily conducts heat, because I frequently vape in long chains of puffs. You will also want to be certain that you get a travel tip in a softer plastic or silicone. It's far to easy to hit your front teeth whilst moving in a car for example.
Whatever you decide, make sure you keep everything clean. You can spread strep amoung other users and back to yourself for example. So, clean your tips, tanks, atomizers and parts frequently and thouroughly.