If you use EM pumps on your investigations, I suggest looking up rspen4462 on eBay and finding one of these pumps that he builds and sells. I've used several different EM pumps over the years, and this is hands down the best that I've brought along on an investigation. It puts out so much EM that it will blank out a Mel Meter because it's putting out over 20k mg! You can adjust it's speed and it even has a tripod mount on the bottom. If you do get one of these, you'll be throwing your other EM pumps into the trash can!