Humboldt's Flame Test Burners are designed to be used as ignition sources for small-scale burning tests, such as the UL flame test and other similar test standards. Burner produces a clear flame of any desired height from 1/2" (12.7mm) to 12" (305mm). The burner consists of a threaded aluminum air control sleeve and precision machined, fine-pitch brass needle valve with internal stuffing box and self-sealing packing. The brass mixing tube ID is 3/8" (9.5mm) and overall height is 6" (152mm) A rustproof 3-1/2" (89mm) octagon-shaped, plated die-cast base is also utilized. *Note: CFHs and BTU Outputs are figured on: 5 inch Water Column Pressures for Artificial and Natural Burners. 11 inch Water Column Pressures for LP Burners. Inlet OD for all Burners: 5/16" Serrated.