5.5mm magnet, 8mm Lobster These are 1.5x stronger than our 4.5mm ones.These will lift 565grams before separating.Absolutely the strongest we have found in this size range. This clasp is: 5.5mm diameter X 19.5mm, including 8mm Lobster 7/32" X 3/4", a penny coin is 19mmComes with Heavy Duty 4mm 20ga open jump ring We won't sell them without a jump ring, as there pretty much aren't any clasps that would attach to the opening attached to the magnetic section. In our opinion, suitable for chains up to 40grams. You be the judge for yourself. No hassle returns. Spring ring and other clasps WILL be slightly attracted to the magnet, as their internal springs are steel. Rest assured these are solid 14k NOT responsible for any losses due to clasp failure. USE AT YOUR OWN RISK if you use a PACEMAKER, INSULIN PUMP, OR DEFIBRILLATOR etc...Thanks Weight: 1gram each DO NOT clean Magnetic Claps in ULTRASONIC cleaners as it will reduce the strength of the magnets.