I got one of those but a couple of times I am sure the tip moved when I was machining, I think I must be loading it wrong. All the other ones I have the tip is secured via a hole in the middle.
I have bought some 20x20 holders off fleabay and machined them down to fit my holders, takes a carbide cutter to do it but they are always cheaper on fleabay than 12mm or 10mm ones. All I need to do now is find some wayof reducing the diameter of carbide milling cutters larger that 1/2" dia then I will be laughing (perhaps I should get a larger mill better still larger workshop)

Peter