This Adox Small Darkroom Thermometer is an accurate mercury free thermometer.
This glass thermometer measures 15cm long is much more accurate than cheaply made and overpriced digital thermometers. The temperature measured range is 15°C – 40°C in 0.5° increments.
It fits in most Paterson-like developing tanks, and all trays, so you can control the temperature during developing.
It comes in a soft plastic case.
The Brownie Camera Guy says:
I have tried a few digital thermometers, because I want to use them, and I always return to glass analog thermometers. This one is a straightforward and extremely accurate thermometer. There’s no mercury in case it breaks. I have a couple of these in my own darkroom.