The Gunners finished top of the table in the league phase, winning all eight fixtures, scoring the most goals and conceding the fewest of all 32 teams. A top two finish was then made official after a 3-1 victory in the San Siro, meaning Arsenal are now assured of hosting the second legs in all of their knockout matches.
Saracens will travel to face Bath in the round of 16 after being beaten 28-3 by Glasgow in their final pool match at Scotstoun. Most of the points came in the first half, with the Warriors scoring three converted tries through Ollie Smith, Kyle Steyn and George Horne while Saracens replied with an Owen Farrell penalty. Seb Stephen then rumbled over in the closing seconds of the match to secure a fourth successive bonus-point pool-stage victory for Glasgow.