Pre-made. Micro Arts Studio's Urban Fight series (basically, "combat damaged" version of their Urban series bases).
They looked too elaborate compared to CB's tactirock but so Infinity themed that it could be home made. Thanks for the clarification.
That's a nice design. Maybe the best redesign for IS so far to me (the whole box with the Bao is my favourite). Thank you @Errhile for the answer After several tests, I use those bases (both Urban Fight and Urban) for all my Infinity miniatures because they allow to easily adapt/conceal the various tactical things CB put under the mini. Depending of the base, it's also possible to remove the tactical rock and still adapt the mini. Example. This is also the case for the Bao Sniper where the tactical wreck is cut and positionned differently. Those bases also have several wide versions allowing to place miniatures that are spreading their legs without them briming over the base.
