Yes, umbrellas are allowed, but would need to be compact enough to fit under your seat.
Umbrellas of all shapes and sizes arepermitted in Madison Square Garden provided they will not interfere with other guests movement or enjoyment of the event and fits comfortably under your seat as MSG does not provide an area to check bags, coats or any other personal belongings such as anumbrell
I'm pretty sure they are but from my experience it would be venue depending. I'd call it check their website to be sure
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