What gauge wire is typically used for the input to a home breaker box?
In the 2011 version of the National Electrical Code, there was Table 310.15(B)(7). This table was quite handy for determining the service conductor size.  In the 2014 version, it looks like they've done away with this table. However, the long code trail that has replaced it, seems to basically say the same thing.

National Electrical Code 2011
Article 310 - Conductors for General Wiring
II. Installation


Typical services (in the US) are 100, 150, or 200 ampere (though 60 is common for older dwellings). Which means you'll be dealing with a possible range from 4 AWG copper to 2/0 copper (2 AWG al to 4/0 al).  Which means you'll want a device that can accommodate conductors from about 0.3 in. diameter to about 0.7 in. diameter, if you want to cover the whole spectrum of possibilities.