The full name for this is the Flat Cat Gear Ocelot: DIY HX (heat exchanger) Mug Kit. From this you can ascertain that it is a DIY kit. Though there is not a great deal to actually do as it is comprised of one simple metal plate.
This is an adapter plate that converts a little FMS-300T Hornet stove to work with a heat exchanger pot. Heat Exchanger pots have a ring of fins around their base that snatch a few more of those BTUs from the stove and transfer them to the pot. They also act as a windscreen to the base of the pot. By partially dismantling the Fire Maple stove, which takes a grand total of one spanner, it can be reassembled with the adapter plate in place instead of the pot support arms.
The adapter plate from Flat Cat Gear is 0.020″ thick 304 Stainless Steel. I wish it were titanium as the build is a bit of overkill. But it is a robust little adapter plate that will not easily flex. Flat Cat Gear have also made the drawings and dimensions available for anyone who wants to fashion their own. Which was good of them as they had no need to do that. I’m too lazy to make my own and purchased the one they sell.
Once reassembled, the stove weighs 70g and can be left as it is, or disassembled and reassembled, finger tight, as required. The adapter plate is 89mm diameter so fits comfortably inside most pots. While the plate will mate with a number of pots it is specifically designed to nest snugly with the little Sterno Inferno heat exchanger pot.
Heat Exchanger pots are available from a number of manufacturers. The Flat Cat adapter plate works especially well with the 121g Sterno Inferno pot, that will hold 650ml, but is more comfortable with up to 550ml. Or use with the 170g Olicamp XTS (Xcelerator Transfer System) pot that holds up to 1150ml, but is more comfortable with up to 1000ml. Note that the Olicamp pot is a badge engineered (OEM) Fire Maple FMC-XK6 pot. Both of these pots come with overkill lids and a flattened and a cut down foil pie dish is a far lighter alternative. While these pots are not particularly lightweight, the heat-exchanger fins adding weight, a windscreen can be excluded with this system.
I had a glance at a couple of other heat exchanger pots I have. The pot from the fantastic MSR Windburner stove has angled fins in the heat exchanger which prevent it nesting with the adapter plate, so that didn’t work. My old Jetboil Flash heat exchanger pot does fit the adapter. It is not a particularly snug fit but cannot slip off while in use. However it is a tall pot and holds a lot of water. If not using a canister stand, and few of us do, it is a bit of a rickety top-heavy affair when in use and I experimented no further with it as I wasn’t keen on the set-up.
I have not done burn times and weighed canisters before and after heating water as there are far too many variables- temperature of air and water, windspeed, height above sea level etc. But it is patently obvious how efficient this system is, particularly when the stove is only used at a half to three-quarter burn rate.
The Flat Cat Ocelot adapter plate is a simple way to convert the inexpensive Fire Maple stove to work well with some of the smaller heat exchanger pots available. It is not a dramatically lightweight system but it is effective and a far more efficient transfer of heat is attained. The burner head is protected from wind so a weighty windscreen can therefore be excluded. This is not a system that Three Points of the Compass is likely to be using on longer, multi-day hikes, despite the more efficient and reduced use of gas being obtained from it. Instead, it will work well as a lighter alternative to the Jetboil, or similar modular systems, that can be used on day hikes.