You need a high volumetric FOUR gang box (two gang for the 3102, three gang for the 3103 and four gang for the 3104-3106). Raco Adjust-a-box is one such beast. I suggest a plastic, rather than metal, gang box but metal can be used.
Technically, a 3106 cannot be installed in a four gang box due to NEC requirements (you'll "overload" the box).
In new construction here's the better method:
Provide plastic, high volumetric, four gang box at standard switch height for Lutron Grafik Eye. Provide one 20 Amp feed from main panel directly to four gang junction box located 6â€ above floor. Run all switch legs from lights into junction box. Pigtail all commons and grounds together in the junction box. From junction box to four gang box (at switch height) provide one hot leg, one neutral, one ground, and one conductor for each switch leg). This places all pig tails and wire nuts in the junction box and not in the four gang box for the Grafik Eye. This avoids overloading the box as per NEC requirements.
---Your friendly Lutron dealer.
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