Stabila 37816 Type 196 spirit levels, 48"/16" combo set, includes an extra-rigid rectangular aluminum profile with reinforcing ribs and two milled measuring surfaces - suitable for overhead (vial down) measurement. Also includes removable shock-absorbing end caps with anti-slip wall grips. Crystal clear vials readable in any direction with no change in accuracy tolerance. Spring steel hairline indicators in vials. Locked vial system, no recalibration needed. Removable rubber end caps for scribing in corners and for reading tight header and sill openings. Rubber end cap(s) grip walls and do not leave marks. Metal hang hole for storing level on site, and rubber hand grips for comfort and stability. Vial accuracy is guaranteed for life.