I built mine and, not to be cocky or anything, think it is the cat's meow... It is lighter, stronger, cheaper, easier to build and works more reliably than most I have seen...
I sleeve it with an aluminum arrow shaft and use a carbon fiber arrow shaft as the plunger rod. An arrow tip insert is glued in the end and I machine a field point into the piston/cup (this is the only "hard" part but can really be done with a file and drill w/ 20-30 minutes of time). I used a yellow cedar dowel as the body and epoxied the whole thing together. As an added bonus, the piston can be unscrewed to hold a thin metal pick which I use to get the ember out if it gets stuck. I use a black rubber o-ring and some braided fishing line as a seal-breaker so it can be collapsed for storage. I wrap the whole thing in para-cord just for kicks. Carbon fiber is super tough - aluminum tube is super smooth. I hunt with a bow so I use broken or slightly bent arrows - this stuff costs me nothing which is why I say "cheap".
O yea almost forgot - I went through a lot of lubricants trying to find the one that worked well for me- I ended up using common Glycerin (aka glycerol) - doesn't eat the rubber o-ring and is super slick. In the bush I have used the oil on my nose which works (rub it up and down the corner of your nose - gets the job done in a pinch).
I'll see about making a video and starting another thread for this - will link to it here when / if I get around to doing it.
Thanks for all of your interest - we're all in this together.
-XexorZ