Built for situations where standard markers just aren't enough, Avery Marks A Lot UltraDuty markers are ideal for construction sites, warehouses, workshops & more. Avery industrial markers work great on plastic, wood, metal & concrete. The durable tip also works on abrasive, dusty, wet & oily surfaces without clogging. Specially engineered to resist water, abrasion & smearing, the heavy-duty ink makes sure that writing lasts through the harshest conditions. The cap also features a clip to keep markers secure in pockets & to prevent rolling off of surfaces. Marker Ink Type: Permanent; Marker Tip Type: Chisel; Marker Tip Size (text): Medium; Marker Tip Size (numeric) 5 mm.