Wunderlich - Safety Oil Filler PlugEasy handling and effective anti theft measure. Unobtrusive single piece design, without any moving parts. The plug is almost impossible to open without our supplied special key, unlike many other similar versions that can easily be opened with standard tools. The facts: Opens only with a special key. Virtually indestructible single piece construction. Absolutely leakproof. High quality finish. Silver anodised. Key can be attached to key ring.