Most people assume a car with tinted windows is being driven by a famous actor or four spider monkeys. Keep them guessing with today's Groupon: for $140, you get a tinting treatment on five car windows at M&M Glass Tinting — Santa Monica Auto Sound (up to a $280 value).

Amid the stereo systems of Santa Monica Auto Sound, M&M Glass Tinting's staff shields car, truck, and SUV windows from sunlight that damages upholstery and reflections that distract drivers. Technicians lay sheets of Johnson Window Films over cars to make them fall asleep before tracing the precise shape of each pane of glass. Five windows—two in front, two in back, and the rear windshield—adhere to their new shades over the course of two hours. The panels come with a lifetime warranty, and typically last 15–20 years before starting an Internet company and retiring to the Bahamas. Fit to the windows of any personal vehicle, tinting reduces the amount of light and heat that penetrates the glass, making interiors more temperate and potentially reducing fuel costs due to a reduced need to run the air conditioner.

Though M&M Glass Tinting — Santa Monica Auto Sound sometimes features a discounted price online, this Groupon still offers the best deal available.