Oil Lamp Chimneys are slimmerthan most 10″ talloptions, having a bulge that is less pronounced. Thisthinner bulge is ideal for chimney lamp shades. It allows chimney-ring-fitter to slide further down neck, than is possible on most. This provides best position of shade on lamp. Common size base has three inch diameter. It fits many oil lamps from the turn of the century. Clear glass provides excellent light.