From the product description, check product page for current description, price and availability:

This stainless steel thermowell is your best option of monitoring temperatures in the 27L or 55L FermZilla. Since the thermowell installs into the lid, the thermowell will be well positioned in the middle of the fermenter to provide an accurate core temperature reading. On the bottom side of the FermZilla’s lid you’ll find several convenient drill locations already molded into the plastic. The thermowell is long enough to work with either size FermZilla (or other fermenters!), so if you need to cut the tube down a bit, we recommend using one of these Pipe Cutters. The FermZilla will still be pressurizable after installing the thermowell, just be careful to drill the hole no wider than needed to fit the Duotight bulkheads.

23.6″ long (60 cm)
5/16″ OD (8 mm)
1/4″ ID (7 mm)
Made from 304 stainless steel