I had a couple of C451's (sadly stolen :( ) and the cardioid capsules they used were the CK-1. I think that the CK-4 MIGHT have been a variation on that, maybe a hyper-cardioid version (?). A quick check on the AKG home website doesn't list that model in the "discontinued" or "current" sections. In any case, the current C451 is not a modular mic, no screw-in capsules. That means that you are at the mercy of vintage used audio dealers...this could be a very expensive proposition if you decide to get these bodies (C451/452EB) for the capsules..

The patern is a figure 8,so i gonna keep searching for the missing part.Hope to try it soon :D

Best of luck to you! there are a couple of variations...the C452 has a built-in low cut filter (3-position) switch, and a "B" at the end of the model# means that it is black, instead of silver. Get the cardioid-capsule equipped kit and you'll be able to get a great stereo rig going!