The swivel post assembly on these holders provides universal adjustment in both horizontal and vertical planes. Available with inch or millimeter Starrett Dial Test or Back-Plunger Indicators, they save time in shop set-up and other inspection jobs. For use with all Starrett Test, Back-Plunger, AGD, Dial and Miniature- Dial Indicators. Also accommodates similar indicators of other manufacturers. Powerful, permanent magnetic base holds firmly to steel or iron surfaces – horizontally, vertically, upside-down. Push-button turns magnetic force on or off for quick, one-hand set-up and take-down. V-step adapts base to horizontal or vertical arbors and chucks. There is an extra 1/4-20 NC tapped hole in side of base for indicator mounting post. Three precision ground magnetic contact surfaces (plus V-step). Black wrinkle finish on non-working surfaces. Base/Post Assembly with 811-1Z/PT22428.