Double Stacks is essentially a very basic game in which a single innovative feature dominates the game, and there are very few other things of note. I have played Double Stacks for a few hours in order to be able to give you a detailed review of this NetEnt 2018 release, and to be able to say what are the pros and cons of this game. The game has medium variance and a theoretical return to player (RTP) of 96.10%, so basically it feels and plays like most other NetEnt games. Main game and paytable The main thing about this game is the feature that allows the stack to be doubled, which can then bring you ten-of-a-kind wins. Of course, since the game allows that kind of a win, it also means you need to get that kind of wins to make money, and five-of-a-kind wins are no longer enough. Whenever one of four high-win symbols appar fully stacked on a single reel, the symbols will automatically double and you’ll have two symbols on each position on that reel. During the main game the double stack only applies to these four high-win symbols, and during the free spins game it also applies to low-win symbols and, crucially, to Wilds. NetEnt opted to use fruit machine symbols for this game, which may or may not appeal to you. I personally didn’t like it and feel like a chance was missed to make this game stand out. Diamond, Seven and to a lesser degree Bar are the high-paying symbols, Bell is somewhere in the middle, and then you got Cherry, Plum, Lemon and Watermelon which don’t pay much. The price to pay for those ten-of-a-kind wins is that you do need to get them - Diamond pays 1000 coins for ten-of-a-kind but only 90 coins for six-of-a-kind, and 15 coins for three-of-a-kind. Decide by yourself if this is the kind of paytable you want to play. In addition to these eight symbols there is a Wild and a Scatter. Bonus features Three or more Scatter symbols that appear anywhere on your reels will trigger the free spins game. You’ll get 5, 15 or 30 free spins for three, four or five Scatters respectively. As we already mentioned, the added benefit during the free spins game is that all symbols may appear double stacked, including the Wilds. The free spins may be re-triggered for 5, 15 or 30 free spins more, and two Scatters will give you +2 free spins. In addition to the double stacks feature and the free spins game, there is an additional bonus feature that awards cash prizes. Above your reels, the prizes for each of the four main symbols in the game are displayed, and these are 1000x your bet for Diamond, 500x for Seven, 250x for Bar and 100x for Bell. You get these prizes if you fill the entire board with the same symbol, and this is not in addition to the line wins, but is a total maximum prize you’ll get. Conclusion Double Stacks is a game that uses a unique game mechanics to produce all the fun, and some players might enjoy that a lot. The game can pay well if you get your stacks doubled, especially if Wilds are involved, but it’s still a standard NetEnt medium variance experience in which you have to trigger the good wins just to stay in the game. The prizes for a full board win are nice, but other slots give better rewards for a full board win than the Double Stacks slot. In any case, do try out this slot and see if you like it.