These can be very useful for all sorts of designs. You can buy commercial one in green plastic but this is a method to make them whenever you need to for your designs.
You will need: two long bamboo skewers (or satay sticks) for each extender; plastic or glass vial/test tube; pot tape; material to cover that complements your design – wool, paper etc; double sided tape (optional).
Step 1. Place vial at the top of one skewer and attach using pot tape.
Step 2. Position second skewer to overlap first one giving required height for finished extender. Wrap the joining area securely with pot tape.
Step 3. Cover the entire extender (minus the area that will be in your foam or base mechanics) and vial with your chosen material, using the double sided tape if necessary. Here I have used paper ribbon.
You extender is ready to use.