passing same params through several controllers

Model Product
...
#has weight
end

ProductController
def list
  top = params[:top] #positive integer
  #select how many product based on weight from highest to lowest as
much as 'top' element
  #for example: list?top=10, only list the top 10 heaviest product
  ...
end

def edit
  ... #edit product
  ... #redirect to list
end

so in browser http://localhost/product/list?top=10
i will get the top 10 heaviest product
i edit on of the product
then it will bounce back to list?top=10 instead of list

the question is: how can i maintain the params[:top] across several
methods in 1 controller or several controllers?

Thank you

Store in session variable