I'm ordering new seat foam from classic ind for my 67 A body

I need the seat foam for my 67 Valiant and I have never noticed any seat foam U's separate from the seat foam on original seat foam in any A or B body I parted out. Are the U shaped foam pieces needed to complete a set of seats? I have never heard of these and they don't have pictures. Has anyone had to use them? Thanks and Merry Christmas Everybody.

1967 Plymouth Valiant Parts | AK50108 | 1966-67 Mopar A-Body Front Bucket Seat Foam Piece Set | Classic Industries

1967 Plymouth Valiant Parts | MD3003 | 1966-67 Mopar A & B-Body Front Bucket Seat Foams | Classic Industries