Pucks? Slippers? Sounds about right. Mr. Tangas is correct. They come in several sizes. When dis-assembling the valve gear they should be re-installed in the same place! In most cases the majority of rockers will not require any adjustment. If the shims were re-installed randomly it's possible to have several rockers way out of spec. I disagree with ctaylor concerning the possibility of this being the cause of the noise. I've seen it happen many times. On the other hand, I agree with his statement that one of the new compensating elements (that's the "official" MB name) could be bad right out of the box. I've seen this happen as well. Before any parts are condemned the basic position should be checked and adjusted. Only then can an accurate evaluation be made