Circular vial with 8-minute sensitivityPrecise alignment of support cavity to the 5/8-11 threaded base plate assures accurate centering of instrumentLaser plummet– accuracy 0.5mm – 15mPush-button switch located close to body prevents accidental turning onCR2 lithium battery (included) provides 10 hrs of continuous operationIncludes: SitePro 1300 Swiss-Style Tribrach with Laser Plummet