Solid, black stoppers contain a high percentage of pure rubber and weigh less than neoprene.

• Resilient and pliable for a long time
• Low in free sulfur
• Can withstand adverse laboratory conditions without hardening

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. Stoppers will withstand temperatures from –25 to 70 °C (–13 to 158 °F). Each stopper has its size marked in raised figures.