Description This battery vent cap provides peace of mind since it has a flame arrestor. Since all lead-acid batteries produce flammable gas, a flame arrestor is an important option. Hence if a nearby spark ignites the gas, the spark arrestor stops the flame from entering the battery where it could ignite the internal gas. You can learn more about this battery vent cap by reading this article on battery flame arrestors. This battery cap will fit on all batteries that have a standard 1/4-turn bayonet vent opening. In addition, we have adapters that will let you mount this vent cap on most other batteries. Thus, if your battery needs a screw-in or push-in type vent cap, choose from the threaded and push-in type adapters that are listed below. Screw-in battery cap adapters: #4D-8D-SIA  Adapter  This screw-in adapter fits 4D and 8D batteries with 7/8″diameter threads. #SE2218  Adapter This screw-in adapter fits batteries with M22x1.5 metric threads. #M27x3-SIA  Adapter This screw-in adapter fits batteries with M27x3 metric threads. It was originally designed to fit an Enersys Varta battery. Push-in battery cap adapters: #4D-8D-PIA Adapter This adapter fits 4D and 8D batteries and any battery with a 3/4″ diameter vent hole. #1050VCA  Adapter This adapter fits into a 1-3/8″ diameter battery vent hole. This adapter fits any European-style DIN battery and some Douglas batteries.