The stainless steel option on Hunter rotors offers mutliple benefits, here are a few:
Vandal Resistance - Parks and other common ground areas that have heavy foot traffic can sometimes create vandal issues with sprinklers, the stainless steel option adds strength to the riser resulting in less replacements and failures.
Coarser Soil Applications - Well suited for installations in coarser soil types. Riser seals can wear out much faster with coarse soil surrounding a rotor, the stainless steel option helps prevent this by providing a smooth surface for the riser seal to interact with.
General Durability- Stainless steel materials have proven time and time again that they are the stronger alternatives to plastics in the irrigation industry.