As usual fluke has proven cost effective and dependable. These gator clips work perfectly on a 66 block, and it also contains a pod of pins for tapping a wire through the insulation. Sound is great, and works through almost any material.  Although there are better ones on the market, fluke has kept to the basics.  By doing away with all the extras that most people do not use the costs are now low enough that I can actually be happy to purchase the device that functions at near the level of the high end ones.