Thermaltake Aquabay M3
 

Thermaltake's Aquabay M3 watercooling reservoir is mounted in one 5.25" drive bay. It has a water level indicator and comes with all accessories required for installation. It was designed to go with Thermaltake's watercooling, but works with other systems as well. Its incredible price of about $25 makes it a great accessory for watercooling owners.

Link:
http://www.techpowerup.com/reviews/Thermaltake/M3