TSP S-Fund: What sector is the DJW4500?

[AV8]

All,

I'm in the process of rebalancing my allocations and I've got a simple question. The objective of the TSP S-Fund is to match the performance of the DJ Wilshire 4500 and they describe it as a "Small Capitalization Stock Index Fund". Isn't the DJW4500 weighted more heavily toward the mid-caps? How would everyone on this board view the DJW4500 for asset allocation purposes? Covering both small and mid-caps?

Since I'm under-allocated in both small and mid-cap sectors I'm not sure it matters, but I'd like to know anyway. BTW, since it will be a large transfer from the C Fund (S&P 500) to the S Fund I plan on moving half now and DCA the other half as discussed in another thread somewhere.

Thanks.

AV8