The Viron spark igniter assembly is for the older Viron gas heaters, the 250mj 350mj or the 450mj. Order a new DSI spark igniter assembly today.
This DSI igniter has no sight glass. Its normally mounted to the top plate of the gas heater. Some earlier models had this igniter but with a “clipped” earthing rod (the middle metal rod). If your replacing one of those then you will have to purchase this new DSI igniter and clip the earthing rod to match.