choose size, HOB refugium for 55

[BigJim]

I was going to get a HOB refugium for my 55 gallon reef. I was wondering what size would be good. Here's the brand that I was thinking of:
http://www.drsfostersmith.com/Produ...ll&Ntx=mode+matchallpartial&Np=1&N=2004&Nty=1

What size would you suggest? Are there better or cheaper HOB's out there?

 

[Ti]

as big as you can fit really

 

[chadfarmer]

Large 25-1/2"L x 4-1/2"W x 12"H

 

[BigJim]

Is the medium a waste of time or is the large just better for more nutrient export?