Solid block acrylic vials resist breaking, leaking and fogging. 300 degree view True Blue vials with top-reading window. Accurate to within 0.0005 In. (inch) per inch in all 10 level and plumb working positions. Rare Earth magnets hold onto ferrous surfaces. Heavy-duty 6061 T5 aircraft aluminum chassis provides durability. eLock Center Vial System is mechanically locked in place and is secured with two-part epoxy. Removable eShock Pro impact absorbing, accordian-style end caps. Accu-Edge2 frame profile is precision milled for greater accuracy. One-piece ergonomic rubber hand grips limit hand fatigue.