Canning funnels have both a wide mouth, and a wide neck part.
They are designed both to rest securely in the mouths of canning jars, and to allow a greater flow of semi-solid or solid items through. The necks of regular funnels are far too narrow to allow the proper flow of foods being canned; the neck needs to accommodate chunks of food.
Canning funnels are inexpensive and come in many different designs. They can be made of metal such as stainless steel, graniteware, or they can be made of plastic. Some plastic ones may be collapsible for easier storage. Older ones may be of clear glass. Most have some form of short handle on them.
The mouth width varies from 10 to 15 cm (4 to 6 inches.) The actual neck part (called the “throat”) tends to be about 5 3/4 cm (2 1/4 inches) wide.
A canning funnel compensates for not having a perfectly steady hand, and reduces spillage and wastage on counter and down the sides of the jars, particularly with jams. It also reduces the chance of food going onto the rim of the jars, which can interfere with the jars sealing properly.
A canning funnel is also useful when filling large jars that you are storing flours, beans, etc in.
North American ones are designed to work with regular-mouth and wide-mouth Mason jars. Some models may also work with some European jars such as Le Parfait or Weck which have different mouth sizes, depending on the design of the canning funnel, and the mouth width of the jar being filled.
Ladle directly into jars with a very steady hand and aim, or if you are canning something such as jams, you can try ladling the jam into measuring jugs and then pouring it into the jars to get the benefit of the spouts on the jugs.