An RJ21X is usually a split (50 pair) 66M block and bracket. There is an Amp connector mounted to the right side of the bracket which is factory wired to the right half of the block. You wire to the left side and install bridging clips to provide continuity to the Amphenol. The bridging clips provide a means to test the pairs.

A more current version of this is a 25 pair Krone block with Amphenol.

I guess technically an RJ21X can be an Amphenol connector by itself but that is not usually done. Also, as has been pointed out a split 66M block with bridging clips and no Amphenol is often called an RJ-21X but technically it is not. I have had a few discussions with Verizon about that since they sometimes like to provide an RJ-21X that way.

That said, there are plenty of such RJ-21Xs with as little as one pair. To answer your question you would simply cut down your 6 pairs in order down the left side of the block.

-Hal

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