The new Uni Dia Nano Smudge-free pencil leads have a lot of features to offer you a convenient use and smooth writing experience. The leads are infused with nano-diamond particles to increase their strength and darkness. The special lead formula enables the lead colours to stick to the paper better than conventional leads. It is also smudge-resistant for using with highlighter pens. The case of the pencil leads features a press slide opening. Just press and slide to open the case so that you won't accidentally drop your leads off. Each pack includes 40 pieces of 0.5 mm lead.