Bundled is $3.62. http://www.interactivebrokers.com/en/accounts/fees/commissionFutures-FOPs.php?ib_entity=llc
The ER2 options on Globex are $3.62 / RT for bundled (on the page cited above, the ER2 futures fall under the "All products not listed below" row). The bundled RT charge for the futures contract is $4.80, and the unbundled is $4.72 on the first 150 RTs, $4.32 on the next 350 RTs, and $3.62 on the next 4,500 RTs.
EDIT: In almost every case it's better to go with the unbundled for futures. There are only a couple of non-USD denominated futures for which you will pay higher commission when using unbundled. The contract volumes noted in the unbundled formula are across all the different products you trade in a month (and remember that the volume charts are using sides not RTs).
Correct on this, I meant unbundled on my original post. This guy uses IB and post a screenshot everyday which shows he is paying 1.81 per side on ER2[unbundled]. www.highprobability.blogspot.com