R905-500 MaxBrite HIGH OUTPUT Heelless 15 1/2" Chimney for MaxBrite 500 Lamps
R905-500 Heelless 15 1/2" High Output Chimney for MaxBrite Oil / Kerosene Lamps . 
Recommended for altitudes over 4000 feet 
brighter light at any altitude.

Older model lamps will use different High Output Chimneys 
See R905-2 Heelless and R105 Lox-On

Other options for better light output are the Light Boosters see N108B or N108N for more information on Light Boosters.