Doesn't leak as in waterproof, or doesn't leak as in cells? I think most Nitecore lights are at least IPX6, and all the newer ones are IPX8. And remember, flashlights don't leak internally, cells do. Lithium primaries and/or NiMH cells and that problem goes away. Unfortunately, if you have already had an alkaline cell leak, that light is probably toast. It is almost impossible to clean up the mess. You can try the cell manufacturer, some will replace the light, some won't.