The Homebuilders sector has been active this week amid the release of the Case-Shiller housing number, and options investors seem to be positioning for additional upside.

The January 23 calls were active in ITB (iShares U.S. Home Construction, Expense Ratio 0.48%) yesterday on heavy volume in the underlying ETF as the product is now challenging late October highs.

ITB has rallied more than 4% in just the past five days, and related ETF XHB (SPDR S&P Homebuilders, Expense Ratio 0.35%) is also breaking out to recent highs. ITB is now a $1.52 billion fund, nipping at the heels at the larger XHB which has approximately $1.88 billion in AUM, and ITB actually averages more daily trading volume than XHB for those that pay attention to the metric (6.2 vs. 5.4 million shares).

Two much smaller funds also exist in the greater Building and Construction category, those being PKB (PowerShares Dynamic Building & Construction, Expense Ratio 0.60%) and FLM (First Trust ISE Global Engineering and Construction, Expense Ratio 0.70%).

The difference in this space comes down to index methodology by provider, as ITB for example has a visibly larger slant toward “true” homebuilders than say XHB. Top five holdings of ITB are PHM, LEN, DHI, TOL, and NVR for example, with some other “non-homebuilders” like HD and LOW making up the number six and seven weightings in the fund.

XHB on the other hand takes an equal weighted methodology, so it has heavier exposures to nonhomebuilder names in comparison to the overall basket than ITB, and top holdings are currently names like SCSS (3.41%), MHK (3.37%), and HD (3.37%).