Due to the Russian war in Ukraine, and the sanctions that have followed, the global market for valves is disrupted. Unfortunately, I have had to temporarily remove the valves from sale with the kits. You can still buy the kits without valves and source valves yourself. Each type (ECC83, EL84 and 6V6) is interchangeable between different brands with no need to adjust bias, so the testing and tone will be the same. This is a great time to try old/vintage valves. Check Ebay listings and other marketplaces.