These 50ml round bottom boiling flasks are constructed of borosilicate glass. These particular flasks have long necks and accept a # stopper. Sold in eaches. These are new and unused. Texas Residents: Under Texas State Law, this product requires a Precursor Chemical/Laboratory Apparatus NAR-120 permit to ship to a Texas address. After purchase, the seller will contact you via email to verify your permit. Failure to provide a valid permit will result in a cancellation and refund of your order.