€¢ Durable cast aluminum construction €¢ Precision milled frame for accurate work surface €¢ Solid set Cat's Eye Yellow double bent vials for accuracy with protective lens €¢ Will not warp or rust €¢ Guaranteed accurate to .0004 in per inch The Sands Level 48in cast aluminum Pro 48-48; durable cast aluminum construction; precision milled frame for accurate work surface."