The MR1 family of Media / Substrate Reactors feature a massive 4-inch reaction chamber .  The extra wide design maximizes water to media contact, increasing efficiency and minimizing dead zones in the reactor.

NextReef Reactors  have the largest capacities around, giving you the ability to run large amounts of media, or multiple products simultaneously.  They're ozone-safe, and perfect for phosphate control, de-nitrification or fluidized sand filtration. 

The NextReef MR1 stands over 14 inches tall... that's over a half gallon, big enough for large reef systems - up to 250 gallons