United Scientific Rubber Stoppers, Solid, #13

These black stoppers are crafted from durable natural rubber that remains flexible over extended periods. They are recommended for use with non-aggressive or concentrated solutions and have low sulfur content. They are available in solid, one-hole, and two-hole versions, capable of withstanding temperatures ranging from –25° to 70°C (–13° to 158°F). Each stopper is 25 mm tall and has its size marked in raised figures. They are sold in one-pound bags.