Will these fit my vehicle's existing wheel studs?

M12 x 1.5 is a common metric thread pitch, but you need to confirm your vehicle uses this exact size before ordering. Check your owner's manual or existing lug nut spec. If you're unsure, measure the diameter and thread pitch of a current lug nut or have a shop verify fitment.

Do these need any prep or sealing before installation?

Aluminum can oxidize over time. Before install, check that your wheel studs are clean and free of debris. Install hand-tight first, then torque to your vehicle's specification—refer to your service manual for the correct value.

What's the weight difference between these and steel lug nuts?

Aluminum is significantly lighter than steel, which reduces unsprung weight at each wheel. The exact weight savings per nut isn't specified, but aluminum construction is always the lighter choice for this application.