Model differences

PETKIT Max 3 vs Crystal Duo vs OpenSky: three cleanup routines

An automatic box can look similar in a product gallery yet require a very different litter and cleanup routine. These three products illustrate the choice: the PETKIT Purobot Max 3 rotates an enclosed chamber over clumping litter; the Purobot Crystal Duo rakes a proprietary crystal tray; and the PetSafe ScoopFree OpenSky rotates a clumping-litter chamber with an open top.

Choose the cleanup mechanism first

When a clumping-litter globe is appealing

The Max 3 keeps the rotating mechanism enclosed while using ordinary compatible clumping litter. PETKIT lists a 76-liter chamber and 7-liter waste bin, and its manual limits particle size to 12 mm in length and 3 mm in diameter. It also lists a low 8.03-inch entrance height, but the current product page and manual give different overall dimensions, so do not use a single online width/depth figure to solve a tight space without checking the actual product. Max 3 includes app-based weight/visit reporting but no camera. The manufacturer does not publish a numerical cat-count rating; the advertised up-to-15-day interval is for one cat, not a multi-cat schedule.

When the open tray or open top matters more

Crystal Duo does not sift clumping litter. It is the right comparison when a cat prefers a more exposed tray and the household accepts PETKIT’s specific disposable crystal tray and litter. The routine is tray replacement and wiping the rake/traps rather than emptying a drawer of clumps. It has a camera and supports both listed Wi-Fi bands, but the manual’s age/weight limits still apply and a camera event is not an individual-cat or health diagnosis.

OpenSky is a middle shape rather than a shallow tray: its rotating sifter stays open above. That can be attractive for a cat that resists an enclosed globe while the household wants clumping litter and a waste drawer. PetSafe’s manual sets a six-month age threshold and a greater-than-three-pound sensor threshold for automatic use; the published maximum-weight guide is 33 pounds. Its app uses 2.4 GHz Wi-Fi and the default cleaning delay is seven minutes. This is a different design from Crystal Duo’s rake and from the enclosed Max 3, even though two of the three keep clumping litter.

Match the option to the cat, not just the feature list

For the Max 3, PETKIT’s page lists a 3.3-to-22-pound range; its manual says the cat must weigh over 3.3 pounds and be older than six months. For OpenSky, compare the manual’s age and sensor minimum with the cat’s measured weight, and do not treat an advertised multi-cat feature as a numeric capacity. Crystal Duo also requires an older/heavier cat but has no stated maximum weight in its reviewed manual. If the youngest cat is below a product’s automatic-use minimum, keep automatic cleaning disabled and use a conventional tray or a supervised transition plan instead of treating a kitten-protection setting as permission to run unsupervised cycles.

Then think about upkeep. A bagged drawer has to be checked and emptied; a crystal tray has to be replaced and restocked. The Max 3 and OpenSky both rely on the litter passing through a sifter and on compatible clump size. Crystal Duo avoids that litter compatibility question only by making its own tray/litter set essential. None is maintenance-free, and none should be selected from a “days hands-free” maximum alone.

Use the finder for essential constraints

Choose the litter system your cat must keep, then set any required age, weight, network or entry constraints. An exact hard-fit footprint is not confirmed for all three models in the reviewed primary material, so measure your room and service clearance rather than interpreting an unknown dimension as a fit. Read the model assessment for the operating plan and its limits: Max 3, Crystal Duo, and OpenSky.