From the product description, check product page for current description, price and availability:

An easy way to eliminate chill haze in your finished beer is to add one vial of Clarity Ferm to your fermenter prior to the onset of fermentation. Use 1 vial per 5 gallon batch.

For the beer geek (but still simplified!):
Chill haze is caused in your fermenter during aging when polyphenols and polypetides bond together. Clarity ferm cleaves polypetides (a protein fraction) so they cannot bond with polyphenols (tannin). This product is also known as Brewer’s Clarex.

There are also discussions and testing being done with this product, finding that it reduces gluten levels in beer. Gluten is the protein that Gluten-Intolerant (Coeliac) folks need to avoid or greatly reduce consumption of. Always consult a Doctor first before use in this application.

Features:

An enzyme that is effective at preventing chill haze
Increases shelf-life and product consistency
Does not alter beer flavor or aroma
Has no effect on head retention
Can produce gluten-reduced* beers made with barley (*The majority of beers test below 10ppm gluten when used in the correct dosage)