Light green glass tunnels. Made of green borosilicate glass, the single flare plugs are smooth for comfortable wear. Choose your size: 8 gauge (3mm), 6 gauge (4mm), 4 gauge (5mm), 2 gauge (6mm), 0 gauge (8mm), 00 gauge (10mm), 1/2 inch (12mm), 9/16 inch (14mm), 5/8 inch (16mm), and 3/4 inch (19mm), 7/8" (22mm). Sold in pairs (2pc).