Ah, its a cap. I don't use the caps any more. I use my dynavap tips with various stems or bonger/stem combos and an Underdog ACXL log vape for the heat source. Best of both worlds as far as I'm concerned. With the Dynavap and the iWand I got a lot of flashover or else it took several draws to toast. The iWand has "temperature" settings that don't measure temp at all, they're all timers. So the longer you use the iWand the hotter it gets and the harder it was (for me) to estimate when things were cooked "enough" - various counts after the click aren't very helpful when the temp at the click is already highly variable.
But with the Underdog, I can home in on the setting I want (you vary the heat by varying the supplied voltage) and then you can just set it and forget it. With the stems that come with the Underdog I always got some volcanoing, and with the Dynavap and cap, I'd end up with combustion half the time and under cooked the other half.
With the dynavap tip mounted to a stem and in the Underdog for heat (caps won't fit), it cooks way more evenly. I get very little if any volcanoing and NO combustion, even if using a dynavap tip with my bong and I just set the heater on top there. I left it for 15 minutes once - no combustion. You CAN MAKE it combust by upping the temp at the variable voltage supply, but its readily avoidable.
The dynavap tips let you use regular screens (not the DV screens they are only good for holding up the dosing capsules) and they will always be at the same depth inside that tip - the UD stems you have to make and set a basket screen and I, at least, was never sure I was really getting that basket back in there at the proper height. Always took me a lot of fiddling. Much less fiddling this way and very repeatable from one session to the next.
Ed's Woodscents makes a tip that is supposed to fit in his log vapes and supposedly also the Underdog Alpha - I ordered one over a week ago but its not here yet so I can't say for sure it fits the UD, but it should at least fit Woodscents. Or you can rig an "air lock" at the business end of the stem over your DV tip to fit around or inside one of the other DV models (Alpha, SC3) heater cores, and this does work, but it means you have to remove the tubing every time you refill. I use the bonger adapter to fit dynavap tips into various stems, or they fit straight in to anything with an 8mm ID.
But to use stock Dynavap tips, directly without air locks or adapters,, you need the Underdog ACXL.
