Accessories — such as seat protectors and harness covers — are oftentimes not approved for use with every car seat. Before purchasing car-seat accessories, you'll want to check with the car-seat manufacturer to determine if they have tested the accessories with their car seats, or what, if any accessories, can be used without negatively affecting the performance of the car seat in a crash. Many car-seat manufacturers have even started making accessories that are sold separately, but are specifically tested and approved for their car seats.
While many parents like using mirrors with rear-facing car seats, this accessory can be dangerous if the mirror is not securely attached to the vehicle seat. Mirrors that attach to the rear-seat headrest with suctions cups are the most likely to become a harmful projectile during a crash. They can also be a distraction to the driver if their eyes are on their child rather than on the road.