I purchased the set of crystals from a local retailer to give variety to my scenery. The crystals are very reminiscant of necron worlds -- the crystals are a great idea for such battlefield themes.
In the picture, I've opened up the crystals box. They come packaged in protective styrene for transport and are easy to remove. The crystals themselves are made of semi-transparent green resin that gives them a nice glow. A few of them had a little flash of resin remaining on them (much in the same way there are mold lines on other models). They were very simple to clean up to be honest and not a real problem.
The beauty of this range is that it does what it says: it really is a battle field in a box, ready to be deployed at a moment's notice. There's nothing negative to be said here: the crystals are eminently suitable for use in warhammer, and other 28mm game systems.