The 4" Carrot is 3/8" diameter. What I call the 4" Skinny is actually the 4" Finesse Worm (unless that's been changed). The 3" Regular and 4" Regular are 3/8", the 1.75", 2.5", 3" Skinny and 4" Skinny are all 5/16". The 5" Regular, 6" Regular and 7" Regular are all 1/2", the 5" Skinny, 6" Skinny and 7" Skinny are all 3/8".