need help on sets/ab belt

[fortification]

Questions:
1. I do 12-15 sets per body part once per week, start light higher reps, go heavy with less reps, finish light.
Is this about right to grow?
2. I bought an ab belt called the flex or slendertone belt, I am on level 6 at intensity 50 for 30 minutes and notice abs tightening and defining.
Anyone have any experience with this belt?

 

[InGreatShape]

I was actually thinking of purchasing the slendertone belt. So any info would help me out as well.

 

[fortification]

I like it, I am on a high level now and I try to tense my abs everytime the estim goes on which is every 10 seconds. The slendertone is rated 5 stars by several legit sites but the contour and others have problems.