well i was going to go threw BFS but i see no point in paying for shipping twice when i have to order from aquacave also and can get free shipping

the only bad part is i don't understand what i need

here's aquacaves website for RODI filters




BFS has a package deal and says this is what i get

"This kit includes the same filters which are supplied with new Premium RODI systems. Includes one 1 micron sediment filter, one 0.6 micron carbon block, and one color-changing DI resin refill. All cartridges measure 10" x 2.5" (nominal)."


what I'm lost on is the carbon do i need the 4th one to the right (top row) or middle one on the bottom row ???