Light weight zoom lens

Extraordinarily lightweight standard zoom lens was obtained by chance at the lowest price in the Yahoo Auction. The fact that almost of the barrel fuselage is made of Engineering Plastic was recognized after disassembling for maintenance, glass cleaning and grease-up on moving parts including helicoid and zooming mechanism. 233 gr weight is the lightest in the world, so I imagine, even lens holding ring stopper were done by plastic material, this is why this 35~70 zoom lens weighs very little. The weight factor for camera equipment is much to do with the possibility to be bring out for every photo shooting. The more weight, the less opportunity to take out from the house. And the more distance from the standard focus length, the less chance to be used out side. These were written in "The Leica Manual", published more than half a century ago.