I have encountered several of these rebuilt axles over the years and will not use one again.  Before using these, I have NEVER seen a CV joint fail if its boot was still intact.  I have now replaced 3 joints that started binding with the boots still intact.  Bentley says to never mix up parts between different CV joints (and on the front drive VWs, they even tell you to put the balls back in the same order they were removed!).  I have heard (and seen evidence to support it) that the rebuilders mix and match parts from different joints to make a good one.

Yes, there's a lifetime warranty, but you still have to do the work of taking them out and installing the replacement.

Its too bad the rebuilt axles have become so popular.  I couldn't even buy a CV joint locally.

Bill
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After having done a few CV repacks and boot replacements, I've found that rebuilt half shafts are available from Advance Auto Parts or NAPA for about $100 (plus core) with a lifetime guarantee.  I've gotten them fully packed and covered with a baggie or clean and with a bag of grease.

Unbolt the old one, bolt up the new one, and you get much less grease on your hands.