Toward the bottom of the page, it is listed in the specs as tested:
Application: Sockets 775, 1155, 1156, 1366, AM3, AM2+, and AM2 processors Radiator dimensions: 4.7 x 1.9 x 5.6 inches (120 x 49 x 151 mm) (W x L x H)
Block height: 1.1 inches (29 mm)
Fan: Two, 120 mm
Nominal fan speed: 2400 rpm
Fan air flow: 110 cfm
Maximum power consumption: Not informed
Nominal noise level: 43 dBA
Weight: 2.4 lbs (1.1 kg)
Extra features: USB control
More information: http://www.antec.com
Average Price in the US*: USD 120.00
I'm pretty sure these dimensions are listed on about any site that sells or reviews this product, so a quick Google search often will net you the answer.
120 x 49 x 151 mm, so, I'm thinking width is the 120mm, 151mm is height. This would mean you are going to have about 15.5mm extra on both top and bottom, but it looks like the bottom where tubing is attached, the tanks are a little larger than on top. Maybe account for that difference...
Well- height is 151mm, so your overall height is 31mm larger than the 120mm fan. I'd say you should try to account for 15-20mm on both top and bottom just in case you need a little wiggle room. Like I mentioned before, it averages out to at least 15.5mm for each side, but I think the bottom looks a little thicker than the top due to the tubing and tanks. 15-20mm should get you pretty dang close...if someone else owns the cooler, maybe they can offer the info?