We were sent the Police Station. You can also get the Police Car, Ice Cream Truck and 123 Brownstone. Our set comes with 44 colorful, chunky pieces that are easy for my son's little hands to grasp. It also comes with a small buildable Ernie and Elmo! The great thing about it is that you don't have to follow any rules - you can build it to look like the picture, but the child is also free to use his or her imagination and build it however they choose. The sets are appropriate for ages 2-5 and also include "Play and Learn" activity sheets for additional building ideas.
I had never heard of K'NEX before this, but I am impressed with the variety of building sets on their website. It seems like they have sets suitable for all ages. Also on their website, you can enter to win $1,000 worth of K'NEX building sets in the Make a K'NEXion Video Contest. Check it out and have fun building!