Strong Hand Tools - Str-7089 , Heavy Duty, Adjust-O Magnet Square, On/Off Switches, Pull Force: 160 lbs, 6" x 5-1/8" x 1-3/8", MSA48-HD: Magnetic Sweepers: Amazon.com: Tools & Home Improvement
O Ring Shaped Magnet - ALB Materials Inc
Magnetic Teaching Tool Magnet O type magnet Ring D 29x10x6 mm blue red Student educational levitation magnet|magnet ring|magnet educationmagnet magnet - AliExpress
Y30BH Ceramic Ring Magnet - 50mm O.D x 25mm I.D x 10mm thick - 11.03lbs Pull