Kreitler Flywheel

Flywheel allows for more fluid pedaling like riding outside

First, I have both Right and Left flywheel. I know it's an overkill but it allows for better experience when improving my bike handling skill at times when I can't ride outside. When you stop pedaling, front and back wheels keeps spinning to provide the inertia to help you with balance. They are somewhat heavy but if you train a lot indoors, this is a good investment.