After looking at the thermowell options for the Speidel 30L fermenter I couldn't see spending $30 to $40 on either of them. Bought a spare cap and a #6.5,two hole ribbed silicone stopper and made one up for $10 and about 15 minutes work. Needed to drill a hole between 1 1/16" and 1 1/4" in the cap. Didn't have a hole saw the right size, so used the 7/8" one that I have and then used a 1/2 round file to enlarge the hole to 1 1/16". Smoothed it out with emery and inserted the stopper. Will use one of the thermowells that I already have Both have #10 stoppers, which weren't a fit for the Speidel.