PVA Foam Stoppers
 
Whilst nothing beats the old-school classic "Test tube" setup, these funky blue PVA Foam Stoppers are a great twist to provide a humidity gradient within your tube.
 
Additionally, due to the material of these, mold tends to grow at a much slower rate than on cotton fibres.
 
In order to use effectively, allow to soak in warm water for 1-2 mins before using. 
 
Specifications
 
Colour: Blue
 
Size: Fits all tubes with diameters of 15 & 16mm.