I'm also all for the non-solid, "inner collar" type of knob. The buttons I received from Stu where the solid type without the inner collar. These were fine, till a hot summer day, when pushing in for a knob-press, I felt the knob sink farther onto the shaft a little farther, I guess the hot summer heat softened up the knob material, and now that knob will fall off if I hit the backside of my emepg, Sometimes it will fall off while just bringing the empeg from my car to my house. Also, I can't press in the knob without a small piece of plastic between the shaft end and the inside of the knob.

If you’d like, I’d be happy to take some pictures of the backside of those knobs.