A Chimney fitter, also referred to as a hurricane fitter is not very common anymore, but is necessary if you have a lamp requiring a chimney. Generally, antique lamps--especially oil lamps (hurricane lamps) require the chimney fitter.
The chimney fits directly over the glass opening at the top of these kinds of lamps. The inner diameter of a standard chimney fitter is slightly less than 2 3/8", however you may order your shade with a larger inside ring size by selecting a custom fitter and then specifying the required size of the chimney ring.
You may order this item as a ring (without ordering a shade). To do so, simple configure the options and add the item to your cart.