Do I need to replace both sides at once?

This is the left side only. Depending on wear and your vehicle's history, the right knuckle may still have good life left. Inspect both sides and replace as needed — there's no requirement to do both together.

What fasteners do I need to mount this?

This assembly bolts at the factory suspension attachment points. You'll need the fasteners that originally held your OEM knuckle — typically control arm bolts and strut mounting hardware. Check your service manual for torque specs and any hardware upgrades.

Is the brake rotor included?

The assembly includes the brake mounting surface and hardware. Rotors are sold separately — source new rotors matched to your brake system when you're ready to install.