A 100 Watt, 21cm long, fully submersible thermostatic ceramic heater that is inserted directly into your beer or wine to maintain the correct temperature for fermentation in the brewing bin or fermentation vessel (It will NOT fit inside a demijohn, with which a heater belt or pad should be used). The thermostat is easily adjusted and can be set to maintain any temperature in an 20º-32ºC range. Being more powerful than the 50W heater, it can more easily cope with greater temperature differences between the wort and the surrounding air (typically 15-20ºC) often experienced in kitchens, sheds or garages during winter brewing. You may also need to loosely wrap the fermenting vessel in an insulated camping mat as this will reduce the heat loss and mean that the heater doesn't have to work too hard to maintain the temperature.
When using with a brewing bin, it is simply placed over the rim of the bin and into the holder which is held to the inside wall of the barrel by suction cups. The lid is then snapped tight around the rim of the brewing bin, except for the 5-10 mm where the power cable overhangs the rim. Alternatively, you can use a round file to cut a small notch in the rim of the bucket to provide a snugger fit.
Please Note: These heaters are designed for use in fish tanks, where they are usually placed alongside the internal filter/pump system. This causes the "heated water" to be fully distributed throughout the tank. In your brewing bucket, you will not generally get any circulation of the heat (unless you VERY GENTLY stir the beer once or twice a day) and MAY end up with a higher temperature around the heater and a lower than expected temperature reading from thermometers placed anywhere else in, or on, the bucket.
Another arrangement is to fit a bored rubber bung to the power cable and then drill a 25-26mm hole in the lid of the brewing bin. In this way, the lid can be tightly closed all the way round without the risk of damaging the power cable. This is how I used to have mine arranged on my brewing equipment, however as the current design of this heater comes with a pre-moulded plug already attached, requiring you to either slit a bored bung lengthways, insert the cable and then seal the whole arrangement with some silicone sealent, or remove the plug, thread the cable through a bored bung and then fit a replacement plug, I now use the "notch in the rim of the bucket" method.
When using this item with a standard 5 gallon wine fermentation vessel fitted with a 4" neck, the cap, which is predrilled with a hole to take the air lock, isn't large enough to to take a secondary hole for the heater. In this case, you would need to drill a hole in the shoulder, halfway between the handles and then use the heater again fitted with a rubber bung, or drill a small hole in the lid, remove the plug pass the cable through and then reattach the plug before sealing it permanently in place with some silicone sealant.