Dumpy feeder with spring

Is it similar to this 'Nosloc' feeder?   http://www.nosloc.com/ (I really enjoy watching the happy chickens in the video. )

I haven't used one myself but I've heard good things about them.  Even my local zoo uses them to feed some of the birds in their exhibits.

Something to be aware of, is that you need the right sized food particles for the food to move through the spring part properly.  If anyt of the particles are too big the spring can ge blocked and this will stop any food coming through.

Another thing I have heard is that it doesn't always prevent wild birds getting the food.  They either wait for a chicken to activate it then eat the grain off the ground, or some birds even learn to fly up and activate the nozzle themselves.