They are easy. Go to a bicycle shop and buy a cheap or used brake or shifter handle & about 8 or 9 feet of brake cable & sheath. Go to the hardware store and buy a few inches of ball chain & couplers with a lollypop coupler(the one with a hole in it), and a small u-bolt (like you use for repairing fences). Mount the lever on your shift lever & route the cable down your shift lever, up & over the top of the engine and follow your existing throttle cable. Drill a couple of holes for the u-bolt, bolt it down & use the ball chain to link the hand throttle to your throttle linkage. Aaron can possibly supply a couple of pics of his (that i did) or i might have a few shots of mine in here someplace if you search. It's easy & costs about $15 that way. Or, you can spend $40+shipping for the RE one, and follow the instructions.