The 550 is light, very light, and is well suited for travel, but only in the USA, unless you want to chance frying the innards using an adapter for another country.  It can run off of the 4 (not included) AA batteries, or the included wall plug.

Front View

We like the 550 very much.  The sound quality is very good for a unit that is so light.  Volume can get very high, but with any light unit, you chance getting some vibration noises when it’s cranked way up.  We recommend keeping batteries in it because the vibration usually comes from the springs that hold the batteries in.

Sound Buttons

The 550 offers six sounds:
Ocean Surf
Stream
Rain
White Noise
Summer Night
Wind 

Volume and timer knobs

Slot for optional sound card

You can buy optional sound cards for this unit.  They are offered across the web for about 25.00.  They give you more sound options.  Just make sure you order one for the 550 and not the S650.  They both offer sound car options, but the cards are different.

The volume and timer selector knobs feel cheap.  They feel like they are attached by a spring as they ‘float’ around.  We tried to pull them of but could not.  So that’s a good sign.  We like the 30, 60, 90 minute or continuous selections.  Some units usually only offer 60 minutes.   There is also a headphone jack.

Back view

The table stand bracket snaps into the back and has to be removed to put in new batteries.  Not a big deal as it comes off very easy, not like some cell phone battery covers!  There is a hole so you can mount it on a wall.  Kind of weird, but you may want this option if your night stand is already full.

You’ll find this unit priced across the web for about 49.95.  A fair price we think.  Feel free to add your own review below.