Precision-machined 304 stainless steel tubing forms the Iris cage's curved design, which wraps further around the bottle circumference than King Cage's standard straight-wire cage. This extended wrap increases contact surface area between cage and bottle, creating tighter retention that prevents bottles from bouncing loose on rough terrain. The Iris design works particularly well for downtube mounting where bottles experience more vibration from direct frame contact. Hollow stainless steel tubing keeps the cage at 48 grams while providing the stiffness needed for secure bottle grip without the flexibility that causes aluminum cages to loosen over time.

Each cage is hand-welded in King Cage's Durango, Colorado shop using USA-sourced materials. The stainless steel construction resists corrosion and won't leave black scuff marks on plastic bottles the way aluminum does, though some users report minor scratching on plastic bottles when the cage is tensioned too tightly. The cage accommodates standard cycling bottles plus metal bottles like the Mover 18oz Purist, Klean Kanteen, and Hydro Flask that measure 2.9 inches across the bottom. The Iris doesn't work with Thermoflask 24oz bottles due to dimensional incompatibility. The tighter retention means bottles require more vertical force to insert and remove compared to standard cages, which eliminates side-loading bottle access that works with looser-fitting designs.

The Iris provides more secure bottle retention than King Cage's standard stainless steel cage while weighing the same 48 grams. If you're running downtube cages or riding conditions where standard cages have let bottles rattle loose, the Iris addresses that problem through its curved wrap design rather than simply increasing spring tension. The cage maintains consistent retention throughout its service life rather than gradually loosening like plastic or aluminum cages. King Cage hand-makes every Iris cage in small batches rather than outsourcing production, which gives them direct quality control over the hand-welding process and material selection.