These Bic Velleda Whiteboard Markers feature ketone-based ink that glides on smoothly and erases just as easily, and is low odour to ensure comfort when writing extensively. It features a strong acrylic tip that will not bend or retract into the barrel, even with heavy use. The chisel tip delivers a variable line thickness between 3. 7mm to 5. 5mm, perfect sketching diagrams or creating bold titles.