My buddy is a machinist, and is lightening a few flywheels for me right now. He took my stock D16 flywheel from 19.9 lbs down to 14.5 and it could go another lb lighter and still have PLEANTY of metal left. He said he'd be selling them (if there's interest) for 100 plus shipping. Let me know if you're interested, and what type of engine/car you have.

 

I forgot to mention, no core, and yes, they are balanced.