Keson Screeding Level Set 2 Focus-20 Vials 78" & 39"Features: Break resistant acrylic block focus vials with 20% magnification and luminous backing Rugged 6063 aluminum alloy frame provides the highest accuracy for a perfect measuring result Wide handles for use outside of the screeding area Support beam runs down the middle of the interior for strength Lifetime guarantee against leakage and fading of vial with proper use of the level, vials will neither leak nor fade in the sun