Graham-Field RJ4300-KNOB-2 2-PC Arm Adjust Knob Rollator

Will these work on f-22 rollator gv974bk-t?

I ordered this on dec 9 with promised delivery by year-end. it is now jan 24 and it has not even shipped!! please advise why & when i can expect it?

Is this part compatible with my Medline rollator?

Will these work on the RJ4318?