United Scientific® Rubber Stoppers, Solid, #5 1/2-UNITED RST5A-S

These black stoppers are made of solid natural rubber that stays pliable over a long period of time. Ideal for use with non-aggressive or concentrated solutions. Low sulfur content. Withstand temperatures from ‚Äì25 to 70°C (‚Äì13 to 158°F). Available in solid, one-hole, and two-hole versions. Each stopper has its size marked in raised figures. Sold as one-pound bags.