You can use the RED RUBBER STOPPERS as used in the Laboratory bottles. Be sure to use the most Natural Rubber possible. DO NOT USE SYNTHETICS OR NYLON MATERIALS. You will find that they will contaminate the cell,and break down. Ebonite as used in Transformers as OK but getting harder to get. The Acetyl Plastic seems to be OK but that does not say other products aren't better. Try to use a material that is inert and does not take on an electrostatic charge.
Be sure to cut the 1 inch Spacer lengths in a lathe or by using a jig that will cut square and smooth. We supply 16mm Diameter rod to fit into a 12.5 mm space. ( 1/2 inch ) Use a bench grinder with a fine stone and grind a flat side on the round rod to about 12.7 mm. You be the judge as to the appropriate size for a tight fit. Fit the flat surface of the Spacer towards the Inner Tube and the round part of the Spacer to the Outer Tube.. If you find it is a loose fit you can reverse it for a tighter fit. Be sure to use a micrometer to ensure all are exactly the same, otherwise your tube spacing will be all over the place. Also bevel the bottom flat edge so that you have a lead in edge when pressing in the Spacer between the Tubes. Position the Tubes on a perfectly flat surface to ensure the tops of the tubes are Perfectly aligned.
Another way to fit the Spacers is as per the manual where the ENDS of the round rods are shaped to fit between the Tubes. This is abit more difficult but you can use this way as well.
The Rubber Stoppers are ideal for the outer Tube to Stainless Cannister or Glass Jar Cannister. The compression of the Rubber is good to stabalise the central Tube assembly.
