Fluoroplastic (PTFE) ground joint (NS) sleeves, resistant to nearly all chemicals, withstand temperatures between -200 and +260°C, for gas-tight and liquid-tight standard ground joints, suitable for vacuum up to 0.1 mbar. The grooves on the exterior prevent seizing-up of standard ground joints. The BOLA joint sleeves can easily be detached again and are re-usable. No need for vacuum grease.