These are double flared 6 guage 4MM  tunnels . The back is held on with by a threaded nut. The material is Acrylic. A PAIR LIKE THIS WOULD GO FOR MORE THAT $30.00 AT ANY STUDIO. THIS AND ALL MY JEWELRY IS NEW AND HAS NEVER BEEN WORN. THE PICTURE DOES NOT DO THIS PIECE JUSTICE.   I ACCEPT PAYPAL PAYMENT. THANKS AND HAPPY BIDDING. m002 black