Alvin 240B Series 12" Bamboo Architect Triangular Scale Professional-quality scales with a bamboo core, white high-impact plastic laminated faces and tapered edges. Machine engraved divisions and color-coded furrows. Supplied in hard plastic case. Double numbered. All engineer scales have the following graduations unless otherwise noted: 10, 20, 30, 40, 50, 60 parts to the inch.