Aladdin brand "Heelless" chimney. Fits Models 3 thru11 &model 23 (for use with heelless chimneys).2 5/8 inch by 12 3/4" height, 3" bulge(Aladdins #R910). BP57948 for lower$(ALADDIN HAS A NEW LOGO ON THE TOP OF THE CHIMNEY--THIS LOGO IS OBSOLETE