FYI found replacement o-rings for the hoses and filter pump for the intex pools. I have an 18x48 easyset, not sure if the ultra frames have the same size but I'd guess most Intex are the same.
It's a number 25.
1-1/2" OD, 1-5/16" ID, 3/32" wall or
38mm x 32mm x 2mm
Purchased mine at Menards for $0.52 a piece, probably similar at other hardware stores.