TERM
Feed group
Bookmakers that get their odds from the same supplier: their prices match, and they never form surebets with each other.
Fonbet, Pari, Bettery and Zenit run on one line; the crypto platforms Duel, BC.Game, Roobet, CSGOEmpire and Reels share another; Shuffle and Gamdom take their odds from the same supplier, as do 1win and Mellstroy. Differences between brands in one feed group come only from different update timing and last fractions of a second, so Dozor doesn't show such pairs as surebets.
Knowing the feed groups also helps when you choose bookmakers: two brands from the same supplier give you one view of a match, not two.
Example: Fonbet offers 1.85 on a team to win, and Pari offers 1.87 on the same team. That isn't two opinions about the match but one line that the second brand updated a second later; the opposite outcome is shared too, so there won't be a surebet between them.