The 2500 series Roto Chip bait holders are for baitfish 6 to 7 inches long.  The larger bait takes the bigger fin (3/4 inch high) to get a good rolling action at trolling speed.  The rear hook on this model is also extended back so that it rides at the tail of the larger baitfish.  The hooks are size 5/0. It is best not to place the hooks into the bait.  Let them swing free.  This allows the bait holder to spin with more erratic wounded fish action.  For 4 to 5 inch bait you should use the 2300 series Roto Chips and for 2 to 3 inch baitfish you should use the size 1 2100 series.  For models with barbed hooks, call up the E-Rotary models.
To mount bait in the Roto Chip holder, slide the wire clamp toward the front of the holder.  The holder will spring open.  Lay the bait in the jaws and slide the clamp to the rear until the baitfish is held in place. The most popular Roto Chip colors for salmon are clear, red and chartreuse.  If one color is not catching fish after 30 minutes or so, try another color.  On some days one color will dominate all the others.  The stainless tube in the front of the Roto Chip is the electronic EChip.  As the baitholder rotates, the EChip discharges a tiny electric pulse that exactly duplicates the nerve pulse of a wounded baitfish.  This results in more fish and bigger fish.  The EChip never wears out.  To learn more about it go to www.protroll.com and call up the EChip.