Whoah I am a bit surprised to hear comments suggesting Deca over EQ. Its a medically proven fact EQ has more positive effects than Deca with less occurance of any negative side effects. It dramatically increases your appetite and you said you are looking to gain mass so "Dramatically increasing your appetite" is what you are looking for.
Check out this link and look under EQ and you will see what I am talking about.
http://www.bodybuilding.com/fun/catsteroids.htm
So in short if you can get it ALWAYS choose EQ over deca during the offseason. For obvious reasons increased appetite is counter intuitive during the diet.