It's a frustrating feeling to spend considerable money on an expensive product such as a Nike golf shirt only to eventually suspect the product is counterfeit. Upon being scammed, consumers typically have little recourse, short of filing a police report and hoping for the perpetrator to somehow be brought to justice. Instead, teach yourself to be a more wary consumer and avoid purchases of counterfeit items in the future.
Check the label inside the shirt and any lettering on the inside or outside for spelling errors. An authentic Nike product won't contain any errors of this nature, but it's common for low-end counterfeit products to have one or more words spelled incorrectly. The shirt also should have a tag free of errors.
Compare the shirt with a similar Nike product that you know to be authentic. For example, if you find a suspicious shirt online, find the same shirt on Nike's website or on the website of a reputable Nike dealer. Look carefully for subtle differences, such as color, the width of stripes or the placement of logos or lettering.
Examine the Nike logo on the shirt and compare it to Nike's actual logo. In some cases, counterfeiters are unable to exactly reproduce brand logos. The angle, slope or proportions of the logo might be slightly off.
Ask yourself if the seller of the Nike shirt is a licensed Nike dealer or something else. Counterfeits of brand-name products are extremely common online and from vendors who use a temporary location such as their vehicle or a kiosk at a flea market. If the shirt is being sold at a licensed Nike dealer, it's likely authentic. If not, the chance is too great that the shirt is fake.
Compare the price of the shirt with Nike's suggested price for the same product or a similar product. Although some legitimate businesses sell authentic products for less than the manufacturer recommends, this different should not be dramatic. For example, if Nike's price for the shirt is $60 and the vendor is selling it for $15, this is a sign of its lack of authenticity.