A funny thing happened on the way to preparing this review. I could not find this item on the Quickboost web site, the Aires web site on on any of the on-line retailers that I normally buy from. However I did find it listed with Super-Hobby for $7.43. For those modelers wishing to purchase this set you may need to search to find a supplier.
Background (from Wikipedia)
An infrared search and track (IRST) system (sometimes known as infrared sighting and tracking) is a method for detecting and tracking objects which give off infrared radiation, such as the infrared signatures of jet aircraft and helicopters. IRST is a generalized case of forward looking infrared (FLIR), i.e. from forward-looking to all-round situation awareness. Such systems are passive (thermographic camera), meaning they do not give out any radiation of their own, unlike radar. This gives them the advantage that they are difficult to detect.