TWSBI Precision Retractable (RT) Pipe Mechanical Pencil - 0.5mm - Matt SilverWith over 20 years experience in making mechanical pencils, TWSBI knows how to make them to last. Constructed from all metal parts internally and externally and uses a super long built in eraser so you aren't replacing them often like in some other brands. The RT Pipe model has a retracting lead feed mechanism so the pencil tip and lead are protected when not in use. Lead size 0. 5mm