What I use and strongly recommend is what MMM sells at 650 Central: the original Race-Tech cartridge emulator, designed by Paul Thede, and made in the United States. With those emulators you also get Michael Morse's expert tech support and installation instructions. Tech support is also available from Race-Tech.
At Mike's XS you get a Chinese knockoff that lookee right and nothing else--no instructions, no tech support, nothing but the hardware. Of course if you know enough about fluid dynamics to work out the damper rod modifications needed to install the valves, you don't need instructions or advice.
A critical part of the emulator is the spring that controls the valve. The rate needs to be right, and no one to my knowledge has done an inspection of that part on the pirated valves.
Cartridge emulators are not "drop-in" parts, and installing them with dual rate fork springs is a waste of time and money. Don't bother to look for off-the-rack single rate springs for our application; they don't exist, you have to have them wound. A wonderful source for springs and emulators is Traxxion Dynamics (
www.traxxion.com ); the folks at Traxxion can have springs wound to match your rider weight, bike weight, and riding style, for a very reasonable price. If their estimate of the correct rate is off, they'll make it right. Their tech support is first-rate, too--great folks to do business with.