Round bottom, four-neck flask with outer joints and a thermometer joint.Supplied complete with a compression cap and a Viton O-ring.For insertion of plain thermometers or bleed tubes with an outside diameter between 5–7mm.Hand-blown from tubing to ensure heavy,uniform wall. ● Material:Borosilicate Glass ● Color:Clear ● The side thread can be inserted into the thermometer ● Excellent chemical durability ● Excellent Thermal shock resistance and physical strength,durable ● joints size 24/40:24 is grinding mouth diameter,40 refers to the grinding mouth height,other specifications and so on ● Accessories:C3507-02 Nylon Cap 13mm;R3508-01 Replacement O-rings #107