No-vig odds are the true win probabilities with the sportsbook margin (the "vig") stripped out — a -110 line isn't really 50%. A Polymarket price is already vig-free, which is why Cobia uses it as the fair probability and devigs Vegas lines to compare. Cobia grades 835 picks in public at 73% so you can check the work; today's free no-vig board is at cobiapicks.com/odds.