On the side of each front seat is a long trim piece which houses the memory seat control panel (seat adjustment buttons). 'Seat Side Panel' is what Volvo calls this part. Due to a poor design, they tend to crack & splinter over time. Made of molded plastic (and some rubber at the rear), a broken casing might actually pinch your leg as you get in and out. The one on the passenger side usually lasts longer than the one on the driver side, but can still take a beating. Luckily, if either side panel is shot, it's a cheap fix with a new Genuine Volvo replacement.
Installing a seat panel isn't hard & makes sense when you start doing it (although your neck can get tired). The back end of the piece has a curved plastic ring which comes free by simply yanking up. The front is held to the seat frame by a single torx-15 screw. Once done, look under the seat for 2 or 3 plastic zip-ties that hold down the wire coming from the control panel, & snip them. Disconnect the plug on that wire, & the panel can lift free of the car. Then take the module out of the trim (three torx-20 screws), swap it into your new panel, & do it in reverse.
These come in a few shades. On 2005 & 2006 cars with a beige interior, panels are designated 'Oak' & are lighter in color than the 'Mocca' ones found on 2007-2014 models (in certain lighting, 'Oak' panels can even look slightly gray). However, all 2005-2014 XC90s with a dark gray interior share the same light black panels.
Below we ask you for your interior color & model year so we can ship you the factory replacement that matches your interior color.