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.
Walmart Eye Center Prices 2013. Getting the best value for your money when it comes to eyeglasses, sunglasses, eye exams, and contact lenses. Back in 2009, I made a post about the prices for Walmart eye exams and eyeglasses. A lot of people have visited that thread and posted their thoughts and comments on Walmart's eyeglasses. Plastic lenses cost $28, but have no anti-reflective coating.