Check the listing for details. (3) 4.5mm 925 Sterling Silver MAGNETIC CLASP Converter Necklace 5mm Spring Ring. Color: Silver, Condition: New with tags. Listed at 15.95 USD. THESE ARE VERY SMALL!!! Please be sure it will work for you, so I don't receive anymore issues them being too small. Thanks! Listing is for 3 of these clasps This clasp is: 4.5mm diameter X 15.5mm, 5mm Spring Ring clasp 3/16" X 5/8" a dime coin is 17.5mm In our opinion, suitable for chains up to 25grams. You be the judge for yourself. No hassle returns. It is strong enough to hold one side & slide all around the Nickel without it even starting to come apart. Clasp WILL be slightly attracted to magnet, as will other clasps. Their internal springs are steel. Rest assured these are solid Sterling Silver 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: 0.65grams each DO NOT clean Magnetic Claps in ULTRASONIC cleaners as it will reduce the strength of the magnets.