I give my girls free choice oyster shell and they get almost all of the empty egg shells that we use. The OS dispenser is 2" pvc and full, it it lasts a long time, 6 months or so. This is for 12 hens. A lot of the eggs have good, hard shells but maybe 20 % have thin shells that break easily. Would not be much concern except we sell about 70 % of the eggs they produce and don't want to let our established customers down. Any thoughts on this?