I bought a Vintage Proto tools one from the 60's. In its red steel box with 5 sae sizes and the pivoting installation wand. Super well made tool. It too has just 5 sizes. Seems like the SAE kits always have 5 sizes. But the metric kits have many more sizes.
Were you able to drive your core plugs in with a socket with the engine in the car? The whole point of this tool was to install them in the car,right?