SPI - Magnetic Uneven-Surface Indicator Bases Includes Holder with On/Off Switch: 

• Designed and manufactured in U.S.A. High quality construction for long lasting service.
• The Magnetic Stand adapts itself to any shape or contour, 8 mm x 1.25 mm mounting hole.
• 70 steel segments independently align and attach themselves firmly to uneven surfaces.
• Single cam lock lever securely locks segments in adapted form.
• Powerful magnetic base 1-3/4 x 2-1/4", capable to firmly grip and lift a 16 lb. steel ball.
• Eliminates costly set-ups to position indicators in unconventional applications.

Magnetic Uneven-Surface Indicator Bases; Includes Holder: Yes; On/Off Switch: Yes; Fine Adjustment: Yes; Base Length (Inch): 2-1/4; Base Width (Inch): 1-3/4; Base Height (Inch): 2-1/4