The M6 combines the silhouette of the Leica M3 and Leica M4 with a modern, off-the-shutter light meter with no moving parts and LED arrows in the viewfinder. Informally it is referred to as the M6 "Classic" to distinguish it from the "M6 TTL" models, and to indicate its "Classic" M3 dimensions. The top and bottom plates were made from lighter, cheaper magnesium alloy rather than the heavier machined brass of the M3 and M4. The M6 and M6 TTL are mechanical cameras; all functions save the light meter work without batteries, unlike the succeeding M7, which needs electrical power to operate properly.