The clear no flare bar retainer is hand blown by Glasswear Studios. The 18g and 14g are made from fused quartz glass, 16g and 12g are made from borosilicate glass. The simple straight bar has no flare at the ends. Six clear silicone o-rings are included. Gauge tolerance is +-0.1 millimeter. Please note these are glass and can break if forced to bend. Not recommended for athletic or violent activities. Choose your size below.