Per SI:
All 32 NFL teams can carry 16 players on their practice squad, including six veteran players. That means experienced players across the league may end up on practice squads this season.
Teams are allowed to protect four players on the practice squad every Tuesday. For example, the Bengals can block anyone that tries to poach one of their four 'blocked' players starting on Tuesday. If quarterback Jake Dolegala ends up on the practice squad, there would only be about a 36-hour window — Monday and part of Tuesday — where he can leave Cincinnati for an active roster spot on another team. Once the Bengals choose their four players, no team can sign them to their 53-man roster that week.