Thank you for viewing. These are rollers for making Yaen (a type of fishing lure), for DIY use. There are 20 pieces. They have been tested in actual fishing several times. They roll very well. They are thicker than the rollers I have listed before. The hole diameter is 1.2mm, and a stainless steel rod can pass through. There are 23 colors available. Please specify your preferred number(s) after purchase. The quantities can be mixed.