The Insight has aluminum (bimetal really)
rear drums almost identical to those used on the '84-87 CRX HF. The body of the drum is aluminum, while the friction surface is the typical cast iron or steel or whatever it is they normally use. Instead of relying on thermal mass to deal with heat buildup, they have cooling fins around the perimeter.
I had a set of 1st gen HF drums on my CRX until I converted to rear disk and sold them a few months ago. Some pics I took for the buyer:
They're about half the weight of the stock cast drums.