There is a cylinder with a bar-shaped permanent magnet inside it. And the position of the outer base is a soft magnetic material, which is a kind of ferrite material that is easy to magnetize or demagnetize in the weak magnetic field.
eBay
10/20/30 Industrial Lighting LED Sewing Machine Night Lights Home With Magnetic Flexible Adjustable For Base Adsorbed Work Lamps
Aliexpress UK
Size: approx. 12.1x66.3mm/0.48x2.61" (LxH). It can used for dial indicator and lever dial indicator. Easy using for magnetic base holder. 1 x Magnetic Base Stand Holder. Due to the difference between different monitors, the picture may not reflect the actual color of the item.
eBay
PEO Build Plate Smooth Sheet 235x235 Magnetic Base PET Carbon Fiber Sheet 310 257 Built Plate For Bambu Lab Anycubic kobra 3 Bed
Aliexpress UK
Can hold a DTI by its stem or by a lug. holds the stand firmly (60kg pull).
eBay
USB Powered Red Laser Light Sewing Positioning Lamp Cutting with Magnetic Base DC5V Line/Cross For Sewing Machine Accessories
Aliexpress UK
The magnetic base has the screw hole on the top to install holder for dial indicator, gauge, line cutting, lifting bar and. Magnet has a very strong hold. With the magnet in the on position, it is nearly impossible to detache this base.
eBay
30 Industrial Lighting LED Sewing Machine Night Lights Home With Magnetic Flexible Adjustable For Base Adsorbed Work Lamps EU
Aliexpress UK
Brushless Dust Leaf Blower Vacuum, for Milwaukee M18 Battery 6Speeds Cordless UK. UK 8-9 EU 41-42 Shoe Stretcher Wood Shoe Trees Shape Wood Pair of UK Size. It can used for dial indicator and lever dial indicator, etc.
eBay
Dual Band VHF UHF 136-174MHz 400-470MHz Car Radio Antenna Magnetic Base Car Aerials Accessories
Aliexpress UK
3D Small Round Snowball Maker Toy Children Winter Sand Mould Snowball Fight Clip. 1pcs of Dial test indicator Set. Camping Fishing Stool Ultralight Foldable Stool Beach Stool. One-Touch Cleaning System Kit Design for Weber Kettle Grillfor 7444 Weber Grill-.
eBay
Ender 3 V3 SE Magnetic Sticker With 3M Adhersive 235/310/350mm MK3S 3D Printer Bed Base Build Plate Tape For Creality K1 K1 Max
Aliexpress UK
1 Dial Test Indicator Bracket (Bracket Only, Other Accessories Not Included). Can be used for dial indicators, leverage dial indicators, etc. Three-joint design magnetic. The magnetic can be hydraulically for locked in any position using a knob on the column.
eBay
30 LED Sewing Machine Light Foldable Gooseneck Sewing LED Working Light Table Magnetic Base Light For Drill Presses Work Benches
Aliexpress UK
There is on/off switch for magnet, easy to move the base without the influence of magnetic force. There are fine-tuning device and dovetail groove in the clamping position for clamping various types of dial test indicators.
eBay
NL-770R 144/430MHz Antenna & SO239 Mount Magnetic Base Antenna 5M Cable with PL259 Plug for Kenwood ICOM QYT TYT Anytone Radio
Aliexpress UK