From the Manufacturer
Every sinister Sith should always travel the galaxy with his very own lightsaber. This battery-operated version features a spring-activated blade that extends the lightsaber to more than three feet long at the pr
More Star Wars Clone Wars Force Action Lightsaber Vader from Amazon.com

This lightsaber is not as good as the Obi wan kenobi lightsaber.
The lightsaber hums when turned on.
However, it does NOT make a different sound when swinging in the air light the Obi wan version.
It also only changes sounds when you hit the hilt of the lightsaber but not the “blade.”
I would get a different version next time.
We picked up two for my son and two for my nephew (this one and the Unleashed). This one has a spring action, and is a huge hit with the boys (3 1/2 and 4 1/2) and the dads (heading towards 40). They love that they have the sound built in. It is a bit pricy for what you get (just a mom’s two cents) and I don’t think it will last long, but it makes them happy.
We received an OBI WAN force action light saber for my son on Christmas. My son loved it, but we had no other toy to compliment it. I went online and bought the Vader saber and was somewhat disapointed. Although the kids and I still have fun with both toys, the Vader blade is thinner (not as durable), does not vibrate upon inpact (as does the OBI-WAN unit), and does not glow nearly as brightly.