Storing kennedy half dollars in air-tite cases?

Ive bought a few kennedy half dollars which were loose and i wanna put them in protective cases/packages.Whats the best way? i see some on ebay which are plastic containers with black seal around them and some just sit in a plastic case.some are in plastis baggies an some in plastic an cardboard,MAybe all the same. i understand to stay away from pvc products.thanks