Just started using the SD 825x on my GSP. Started off using the tone then followed by the vibrate when he wouldn't listen. He alerted to the tone but did not respond like I thought he would have with the vibrate. It's almost like he liked it. Haha. I went to the lowest setting of the stimulation and wow he did not like that. But after the first hit he did everything I wanted him to do. He's starting to understand that the tone is the warning before the stim. I'm currently only working on "come" command at the moment. The unit is small but effective. Haven't used it in the field but I'm confident it will do exactly what I want. Just remember baby steps with the e-collar. I only do short sessions and have never had to use the stim more than two times. I purchased the orange collar from Amazon.