Luna Glass Crock Weights, 6.5" (Patented)

Has anyone tried these in the 2-gallon anchor hocking glass crock? how did they fit? were they way too small or did they seem to do the job okay?

What size 4.5" or 5.5" would best fit a standard gallon size with 4" mouth opening and 6 inch inner diameter?

Can i use these for regular cooking? i.e. to keep something submersed in boiling water for an hour or two while cooking?

How many weights are they sending for the purchase price?