Endurance Butterfly Clamps Jewel Chain SPF41. Endurance nipple clamps with jewel chain offer maximum pressure for an intense and localized experience. These endurance nipple clamps feature a fine, silky jewel chain. Non-piercing body jewelry. For first timers please check every 15 minutes to ensure bruising to delicate tissue does not occur. To turn up the volume use a nipple sensitizers like Doc Johnson Novelties makes item number DJ785302. Spartacus A Passion for Quality Catalog.