All the parts necessary to make this GAB are available at Home Depot. There is a total of 5 parts that you will need to purchase. The four in the pics and an extra hose clamp to secure the bottom.

Here is the main part of your Gab. You are not going to use all of it so make sure you have something that you can cut it with. A plain pair of scissors will work fine.

This coupler should be fit inside the other one that you will purchase. Fit in in there with about 50% on each side. I wrapped mine with some duct tape to make the fit and grip better.

This is a drain cover. You are going to cut out all of the grating to make it an open hole. You can leave the grating on if you so desire or you can cut out just a few bars.

The actual drain cover pic. This is the section that you will fit to the underside of your car. Cut the hole just large enough to give it a snug fit going from the outside of the car, through the plastic shield, to the inside. It's pretty straight forward, however, look at the pic on page one to see where to drill your hole. If you look to the left of my hole you can see where I repaired another one w/clear plexiglass. Don't do this!

Here is a pic of the main coupler that you will be using in conjunction with that other cheap looking coupler. You are gong to need both so get both. You will see why.

Just another pic of the coupler. You can see that it is rubber and metal. The other aluminum coupler will slide right in here and make for a really perfect fit with your stock air box and the 3" alum duct. The hose clamps are attached to help with the job. You are going to need one more hose clamp to secure the bottom part of the duct to the drain cover.
Good Luck to all that do this. I really love this mod. My Stillen intake sits in the garage.