Battery Contacts & Coin Cell Battery Holders Keystone Electronics Battery Contacts and Coin Cell Battery Holders accommodate five battery sizes: 5.8mm, 6.8mm, 12mm, 16mm, or 20mm. These devices are surface-mount or through-hole mount and made of phosphor bronze, nylon, or plastic. Keystone Electronics Battery Contacts and Coin Cell Battery Holders are RoHS compliant and ISO 9001:2015 certified.