The Cisco PIX 506E Replacement CPU Fan Kit includes one new fan and four mounting screws.
Compatibility
This kit provides a fan that attaches to the CPU cooling block. If your PIX 506E has a fan that mounts directly to the case behind the faceplate, this kit will not be compatible - instead you want to use the PIX 506 kit. This kit is compatible with:
Cisco PIX 506E (PIX-506E-BUN-K9) with active CPU cooling