Sounds like an incontinence device, but this clever little moulding clips on your oil can etcetera and means you can accurately pour without the need for a funnel. Useful to keep on your oil and coolant top up in the car as takes up next to no space (95 x 40 x 40mm), unlike a funnel! Use again and again. Worth keeping two - one for oil and one for water.
Fits 20 - 50mm bottle necks.