The “head” of abalone indicates the size of dried abalone. It usually means how many pieces of dried abalone per catty (one catty=600g). For instance,
“1 head” means 1 piece of dried abalone weighing 600g; “2 head” means 2 pieces of abalone, average weight of 300g per piece…“25 head” means 25 pieces of abalone, average weight of 24gm each and so on. The bigger the number of head, the smaller the abalone size. The price gap can be huge between different sizes because the bigger abalone will take longer to grow. Please note this term is used for dried abalone only.
For canned abalone, the term “piece” is usually used to indicate how many abalone there are in a can. However, the size per piece is defined by the total drained weight per can divided by the number of pieces inside. For instance, for a drained weight 213g 4pc per can, the average weight per abalone is 53.25g; for a drained weight 130g 4pc per can, the average weight per abalone is 32.5g. The net weight per can is 425g and includes the liquid, the drained weight is the weight of abalone inside the can.