Danish M113s in Afghanistan are, like many other light armored vehicles, using Slat armor (most prominently seen on Stryker armor vehicles since 2003) for protection against RPGs (small rocket warheads with shaped charge explosives). There are several manufacturers of this kind of protection. Two years ago, armor made from aluminum, instead of steel, was introduced. This worked just as well as the steel version, and weighed over a ton less. The lighter version of slat armor, made it possible to use on trucks (both armored MRAPs, and unarmored ones), not just because of the weight, but because LROD can be bolted on, rather than welded on, as is the case with the original steel stuff.
Slat armor is a 2.5 ton steel cage of armor that circles the vehicle. The U.S. Stryker was the first vehicle to use it on a wide scale. Slat armor is similar to anti-torpedo nets that used to protect battleships in port. When an RPG warhead hits, it is detonates between the main armor and the metal slats, and does little harm. Slat armor costs about half as much as ERA (Explosive Reactive Armor), and is about a third lighter, but it is unwieldy. However, in practice, slat armor works quite well, and many other types of armored vehicles, particularly armored trucks, use it as well. The aluminum version is even lighter, and easier to install and remove. This makes it useful in situations where the RPG threat comes and goes.
The Danish RUAG Lasso slat armor is made by a Swiss firm that uses a special steel that weighs half as much as the original steel used for Stryker slat armor.