my favorite genny was always the gmkf20. I love the way the whole thing is one piece of solid stainless steel, from 510 to deck, everything fits together very snug with the o rings, just pop the cap off and slide the tank glass off to rinse it out in seconds. the cap fits so snug that I took one of the 2 o rings off and it's still more than tight enough. it's only 20 mm so it's kind of sleek and I use it on the matching 20 mm f20 mod, this is it in 18500 but I also have the 350 & 650 tubes.
this things got several holes in the deck you can do all kinds of builds but I'm just using a single coil. came with a 1.2 airhole but I drilled it to a 2.0 airhole. vapes nice thick chewy sweet clouds with a 1.4 ohm coil wicked with ss mesh. only reason I don't carry it more is because sometimes of course it leaks. I thought to some day make an air control ring for it to close it off in my pocket
that was my favorite genny but it's been dethroned for me by the wizards wand. titanium with a screw on cap and air flow control. it's just built for a single coil and the deck is awesome, it's got a slight well to it and the single fill hole has a post with a flap that you can adjust from full open to partially or completely closed, it's a built in adjustable tank vent. I drilled this one to 2 mm airhole too but then of course it can be adjusted down from there but I mostly run it wide open. the posts are awesome on this thing, a real pleasure to build, it's 21 mm and light as a feather. I mean really really light, on a titanium wizard evolved II in the same 18500 it feels almost half as heavy as the SS mod next to it.