Canister Shells or 60 Gram Artillery Shells are shells shaped like cylinders. Canister Shells are generally single break shells, but some are double break or even rings affect. The length of a Canister shell will vary from 4 inch up to 7 inches. The length doesn’t specify more powder. All cannister shells cannot contain more than 60 Grams of pyrotechnic material.  So, any shell length greater than 5 inches would be needed for a special effect.