The CP series of PSU's are known to fit in only 3 Antec cases:
The CPX form factor is exclusively compatible with Antec’s cutting-edge Gaming and
Performance One cases, including the Twelve Hundred, P183 and P193. For an updated list of
models supported please visit www.antec.com/cp850.
here's the dimensions:
CP-850 4.7"(H) x 6.9"(W) x 7.9"(D)
SG-850 3.4"(H) x 5.9"(W) x 7.1"(D) (normal size PSU)