Just posted this a few threads down...
I'll measure the water pump pulley tomorrow when I get to the store.
Here's a picture of the Focus Central, Ford Racing and MAC pulleys side by side. All are 4" in diameter. The Ford Racing pulley is the lightest weighing in at 7 ounces. The Focus Central pulley from the 3 piece kit weighs 8.2 ounces and the MAC weighs 8.8 ounces.
The MAC is a painted product, not sure if it's steel or what... Where as the FR and FC pulleys are anonized aluminum. It's certainly not as fancy, and I have no numbers in terms of performance improvement, though MAC says it's a 4 HP gain. It's also nearly half as much as the FR or FC pulley kits. So a good alternative for people looking to say a few bucks for something which once installed, you can't really see anyway...
Hope that helps.