Who uses a decanter any more? They're only seen in 70s cop show offices, sad to say. But the decanter brush is really excellent for any vessel, vase or jug with 'shoulders'. That's why the wire has an angle on it. It allows you to get the brush head down the narrow neck, but with enough welly to really clean the parts you can't reach.
Like all good bottle brushes, it has a cotton tip, so that the bristles won't scratch while they're cleaning.
The brush head is 12cm long with a diameter of 6.5cm. The overall length is 47cm.