They were commissioned by a client to be used with his Sister's of Battle Seraphim, and so would work well with most flying units (Ork Stormboyz, Space Marine Assault Squad, etc).
They feature scrap metal, concrete rubble, pavers, and lots of grit! They are 25mm round bases (standard 40k infantry size).
**** I am currently expanding my range of resin-cast bases. If you are interested in having me design some bases specifically for your army, contact me and we can discuss. This offer is open to international customers as well, as postage should be pretty cheap ;) ***