A proper drop-in air filter for the stock LotusElise/Exige air-box. Despite some great advertising by companies that make fabric/cotton “life time" filters, they are far inferior to a proper foam filter. Foam filters have been used in the racing industry for years. You'll also find them in nearly all off-road vehicles due to their great ability to completely filter air under extreme environments. For those on the race track, you'll often find tire particulates clogging your cloth type air filters, such as K&N and Green Filters, in a single weekend. On the other hand, the foam filters have proven time and time again that you can run them weekend after weekend without service and not sacrifice horsepower. These leaves you with more time and saves money!
Installation and care notes are found here : Tech Wiki