The addi Click Hook set is intended as an upgrade or "booster pack" to the existing Click sets. Each travel pouch contains 8 Addi hooks: 3.75mm, 4.0mm (US F), 4.5mm (US G), 5.0mm (US H), 5.5mm (US I), 6.0mm (US J), 8.0mm (US L), and 9.0mm (US M). Choose the set, or individual hooks to add to your existing Click set.