This is a 4mm-5mm thick silicone rubber heat shield to install on top of the engine.
Why use this? Carb temperature is a critical issue on the Valkyrie - the carbs get hot too fast when there is no air flow. This heat shield allows the carbs to run 15 degrees F cooler than normal under most conditions, helping E10 fuel stay liquid like zero-ethanol fuel used to. Here are some observations on my '99 Interstate: (1) The shield buys me an extra half hour idling in gridlock-style traffic + no wind + 100F air temperature, before the carbs finally get too hot to keep E10 fuel in its liquid state, (2) Engine noise is reduced (reflected noise off the fairing, coming from the top of the engine), (3) Heat soak phenomenon is slowed way down so it appears it is no longer an issue - I have easy hot restarts.
How it works: An air gap is maintained by standoffs between the shield and the top of the crankcase. The heat shield absorbs engine heat that would normally convect to the carbs, when air flow is inadequate. When air flow resumes, the heat shield cools off and is ready for another long stop. The shield is waterproof, unaffected by engine temperature, and is flame resistant. Rain water does not puddle on top of it, because it is hump-shaped when installed. There are no airborne fibers, and the product is cheap.
How bad is the install?
There are two ways to install, from the front and from the side. For the "side install", the radiator is left alone but the engine block is stripped down to bare on top, before the heat shield is put on. In particular, this requires removal of the seat, fuel tank, carb assembly, air box, intake manifolds, smog equipment, coolant tubes and thermostat housing.
For the alternative "front install", you leave the carbs and air box in place, but remove the radiator and thermostat and coolant pipes and smog equipment and four of the intake manifolds. This is probably less stressful, if your carbs are working perfectly and you don't feel like touching them. Of course, you still need to remove the seat and tank, same as for any other procedure you do on this bike.