I am using 4.5mm pure gold ball with 18k gold chain & clasp. 

For the safety reason, clasp and chain is used in 18k solid gold.  

This is only for custom-made order.  There is a 18k solid gold chain inside of  24k gold ball. 

*Metal : 24K Pure Gold, 99.5% (Hall-marked) & 18k gold clasp, 18k gold chain

*24k gold weight: 30 grams

* 18k gold : about 5.8 grams 

*Total Length : 17 - 18 inches(selectable)

*Gold ball: 24k solid gold : 4.5mm

*Leading time 5- 6 days