If you're an avid user of Xbox One's games streaming service Xbox Games Pass, get ready to say goodbye to a significant amount of 360 titles. On May 31, 21 titles are leaving the service's catalog.

Out of the 21 titles on the way out, one two are Xbox One titles, and the rest are from 360. We're not sure why these titles in particular are leaving the service, but we do know that third-party titles aren't permanent additions--though this cut is probably the largest the service has seen so far. Some bigger titles on the chopping block are Bioshock, Bioshock 2, and Bioshock Infinite, as well as Borderlands.

Xbox One

Blood Bowl 2

Defense Grid 2

Xbox 360

Age of Booty

Sega Vintage Collection Alex Kidd & Co.

Bionic Commando Rearmed 2

BioShock

BioShock 2

BioShock Infinite

Borderlands

Bound by Flame

de Blob 2

Dead Rising 2: Case Zero

Dig Dug

Final Fight: Double Impact

Sega Vintage Collection: Golden Axe

NeoGeo Battle Coliseum

Operation Flashpoint: Dragon Rising

Pac-Man CE DX+

Sacred 3

SoulCalibur

XCOM: Enemy Within

Each of these titles will be available on the service until the end of the month. If you don't have time to play them all, you can snag your favorites for 20 percent off.

June's entire list of incoming games hasn't been released quite yet, but we do know that Xbox One exclusive title State of Decay 2 will be hitting the service as soon as it launches on May 22. All members will have immediate access to the game with the service, as well as Sea of Thieves, Gears of War 4, and many, many others. Check out the full list of Xbox Games Pass titles here.