Hook Line & Threader, Inc. currently offers 2 size Threaders, the Standard, and the Marine-Grade Stainless Steel. The Standard Threader is 5 1/2 inches long and the Stainless Steel Threader is 9 inches long.
The Standard Threader comes in Kit sizes #1, #2, #4, #6, #8, and #10. The only difference is the hook size, the Standard Threader is the same size in each kit. The Marine-Grade Stainless Steel threader is sold by itself.
Remember when Threading your bait you are only going half way thru it, so with this rule of thumb, the standard Threader can be used on bait fish up to 10 inches long, and the Stainless Steel Threader can be used on bait fish up to 20 inches long.
The Standard Threader is primarily used for fresh water fishing, and the Stainless Steel Threader for salt water fishing. However, the two can be used in both fresh and salt water.
Some examples of bait for the Standard Threader: Shiners, Night Crawlers, Shrimp, Crayfish, Leeches, Crappie Minnows, Bluegill, Goldfish, etc.
Some examples of bait for the Marine-Grade Stainless Steel Threader: Ballyhoo, Mullet, Pilchard, Squid, Pinfish, Herring, Goggle-eye, Pogies, etc.
And, of course, both the Standard and Stainless Steel Threaders can be used to create custom soft plastic rigs and harnesses.