Since this is the extension for the Hue lightstrip obviously you've discovered that you need your light strip to be slightly longer. It just works (after connecting it of course) and is easy to add to an existing light strip.
You should be aware of one thing though. When you add extensions to a lightstrip it will not deliver more power to the light strip. The overall light output from the entire light strip will remain relatively constant (no matter how long so about 1600 lumens). That means that the brightness of the 2m hue light strip will be lower when extended (adding 2m will mean that it's 1600 lumens over 4m instead of 1600 over 2m). So you should consider doing this for mood lighting or if you would never usually run it at full output. If you require more light in an area you are better off purchasing a second hue light strip.
Increase the length of your Philips Hue Light Strip with the Philips Hue Light Strip Plus Extension for even greater flexibility in lighting your home. Transform your living room, bedroom, kitchen and other rooms with millions of colours and shades of white light. Sync to games, music, and movies for enhanced experiences. Extend your Philips Hue Light Strip Plus (sold separately) up to 32 feet by adding this and additional 40-inch extensions to cover larger surfaces and enable wider applications. The Light Strip Plus Extension is perfect under bars, bed frames, or cabinets, with included adhesive tape. Trim it to the perfect size with the included cut marks. Connect it to a Hue Bridge (sold separately) to control your lighting. Light the entire home with versatile accessories (sold separately) such as Hue Dimmer Switch, Hue Tap, or Hue Motion Sensor. This box includes a 40-inch (3.3-foot) Light Strip Extension and two-year warranty.