People call Joye 510 and its clones, a slim ecig, "510" - I know what you are talking about.
510 is also a threading
510 manuals have good reliability. They are not particularly strong. They have short battery life with those little batteries. But with a totally sealed metal threaded end they are safe from being damaged or killed by juices leaks, and manuals make it easier to get a good hit. I use them with Boge 3 ohm cartomizers. You can use anything 2.5 to 3 ohms on slim batteries.
Janty is an excellent choice - Janty and Joye aka Joyetech are the real 510's.
What you are looking at is a 510-T (tank model with tank atomizer and tanks)
100mah is about 1 hour of moderate
vaping
Joye/Janty 510 is 180mah
If you find the longer mega xl size those are 280mah