TechPowerUp - Alphacool Rolls Out ES 4U Reservoir with D5 Top
 
“Alphacool introduces the ES 4U reservoir with integrated D5 pump top from the Enterprise Solutions series. The combination of pump top and reservoir is designed to be mounted directly into the front of 4U servers. This gives you easier maintenance possibilities thanks to clever positioning in the server case!
 
Another plus point is the cover used, it is made exclusively of acrylic, allowing you to see and control the water cooling level at any time. In addition, the acrylic cover has 2 inlets and outlets with G1/4" threads, which allow easy filling, draining and bleeding of the cooling loop even when installed in the case. The integrated pump top and is compatible with all D5 format pumps. The pump retaining ring, pump O-ring and all screws are included.

MSRP: 109.98€ including VAT. For more information, visit this page.”
 
My thoughts:  This will make it more convenient since it is easily accessible on the racks.  It is a nice innovation from Alphacool.