This clasp is:    

• 4.5mm diameter X 10mm, NO Spring Ring Clasp with this listing
  
           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.
• 
  
• Other clasps WILL be slightly attracted to a strong magnet, as their internal springs are steel.
  
  
• 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