The correct spark plug and gap is crucial to proper ignition. Spark discharge is a breakdown in the air insulator between the electrode and ground. Yes - air is an insulator, a pretty good one at that. As voltage builds at the electrode, atoms in the air within the air gap gain electrons. This process is called ionization.
It's one of the reasons why our standard lenses are polycarbonate (thinner than standard lenses typically sold by other eyeglasses retailers). At Warby Parker, you can upgrade to high index lenses for an additional $30 whereas it typically costs $60 to $100 more.
Prescriptions for contact lenses are valid for 12 months. The average national cost for an eye exam is $114, but the cost will vary depending upon the retailer. Many insurance companies completely cover the cost of an annual eye exam. In some cases a $10 to $30 copay may apply.