Hi, last year I purchased (from REI) the Perception sit on top hybrid kayak. I am interested in getting some accessories for fishing in it. I see that there are two different types of balls that can screw into the kayak. 1 inch or the one and a half inch size. And then I want to be able to attach a fishing rod holder to it. I would like to know which size screw in ball do I need to order? And I an wanting the rod holder too. 
Can someone  get back with me and give me some insights and information please.
or do you recommend that I go to the perception website and order from them?
I would rather order from REI if possible.
Thank you.