If you want to keep the factory airbox and intake system the way it is but add a higher flowing, reusable filter, this is a great option. The aFe Pro 5R filter replaces the stock paper style filter with an oiled, cotton mesh style that is washable and reusable. Filter oil is always slightly better at catching debris than a dry filter. It fits straight into the stock airbox so you can't even notice it's an upgrade on your Subaru WRX 2015+.
The aFe Power limited warranty covers defects in materials and workmanship in every aFe Power product you purchase during the applicable warranty period, subject to certain exceptions. aFe Power warranty period is TWO YEARS, unless otherwise specified in the Warranty Policy, from the ship date of the applicable aFe Power product to you, as determined by the date on the packing slip or invoice. The warranty period is not extended if aFe repairs or replaces a warranted product. aFe Power may change the availability of limited warranties, at their discretion, but any changes they make will not be applied retroactively. For more detailed information related to the limited warranty, please refer to the Warranty Policy on aFe's website or in the supporting documentation that came with your product.
Limited warranties on aFe Power products applies only to the original purchaser of the product and is not transferrable during the warranty period.