I have a couple of the new knobs and I knew they were good because I can hold the knob that is on the radio and swing it around and it is so snug as a rug and does not fall off. Also, there is a center rubber pin in the middle of the knob that fits into the plastic insert to hold the knob.
That was the best selling point of these knobs. A little steep on the price but awesome FDNY knob
Motorola FDNY XTS 3000 5000 Radio Knob | eBay