Ninja DoubleStack XL 10-Qt Air Fryer with Smart Thermometer review

The Ninja SL451 is the DoubleStack version for someone who wants two cooking zones, rack-level loading and a built-in food probe. Its two stacked baskets total 10 quarts, according to SharkNinja, and the Smart Cook thermometer monitors a protein in one zone until the selected internal doneness is reached. That extra automation is useful only if the probe's placement and supported-food limits fit the meals you make. In particular, the manual says the probe works in Zone 2, not either basket at your choice.

Ten quarts still means two separate five-quart baskets

SharkNinja lists a combined 10-quart capacity divided between two 5-quart drawers. Each basket has its own crisper plate and a removable stacked-meal rack, so the manufacturer describes as many as four food positions at once. The appliance still has only two independent cooking zones. The plate and upper rack inside one drawer share that drawer's program; the top and bottom baskets can use separate settings. This is the useful distinction if your plan is a protein and a vegetable in different zones, or several items that can share one zone's time and temperature.

The product page says the layout can fit two five-pound chickens and can feed up to eight people. These are the manufacturer's examples, not an independent fit test or a serving guarantee. A combined volume figure does not turn the stacked drawers into a single 10-quart cavity. Wide or long foods may be constrained by an individual basket opening, and the removable rack reduces the vertical room available in the same basket. SharkNinja lists outside dimensions of 20.83 by 13.07 by 17.72 inches and a weight of 25.35 pounds. Measure the height and side clearance for the tall body, plus the room needed to pull out a hot drawer; the page's space-saving description should not be read as a claim that the appliance is small in every direction.

The probe is useful, but it has a specific job

The included Foodi Smart Thermometer gives the SL451 a clear difference from the SL201. The guide describes Small, Large and Manual probe choices, protein and doneness selections, a display of current and target temperature, and automatic shutoff when the desired doneness is reached. It also explains how to coordinate the probed protein in Zone 2 with a separate Zone 1 program using Smart Finish. The probe is not a second cooking zone, a guarantee of perfect results or a replacement for safe food handling. The guide refers users to USDA guidance and warns against frozen protein and cuts thinner than one inch; it also recommends proper probe placement. Those limitations are more decision-useful than a generic “smart” label.

Because the jack is assigned to Zone 2, reserve that drawer for the food being monitored. If you need to probe a piece placed in Zone 1, or to track two proteins simultaneously, this configuration does not document that plan. When both baskets contain foods that should finish together, Smart Finish coordinates different times, temperatures or modes. Match Cook copies matching settings between zones for a larger batch of similar food. These are different controls: one syncs finish time, the other replicates settings. The probe can be used with the Smart Finish process described in the guide, but it remains a single probe in Zone 2.

Six functions and a tall, multi-part cleanup routine

The SL451 owner guide lists Air Fry, Air Broil, Bake, Roast, Reheat and Dehydrate. It notes that Air Broil is preset to 450°F and not adjustable; the inspected material does not establish a full adjustable temperature range. The guide says no preheat is needed and describes a 1-to-12-hour Dehydrate timer. Those mode-specific instructions are useful, but don't infer the lowest temperature or the range of every mode from one fixed Air Broil setting.

The guide calls the baskets and crisper plates the dishwasher-safe removable parts, while recommending hand-washing to extend their life; the main unit is wiped clean and must not be immersed or put in a dishwasher. It describes nonstick food-contact surfaces but does not identify the basket substrate or coating chemistry, and the product page makes no explicit PFAS-free claim in the reviewed information. There are two drawers, two plates, two racks and a probe to clean and store. If that maintenance burden or the coated basket construction is a concern, consider a simpler dual-basket configuration or inspect an alternative whose manual and material disclosures match your requirement.

What changes from the SL201—and what does not

The related SL201 is 8 quarts total with two 4-quart baskets and the same broad stacked-rack idea, but its exact package does not list the SL451's integrated food probe. The SL451 increases the maker-listed total by two quarts and adds a zone-specific doneness workflow. Both remain vertical two-basket appliances with two independent settings, and neither gives each of its rack levels a separate program. A traditional side-by-side dual basket may be easier to fit under low cabinets, while a single wide drawer may better suit broad foods; those are different layouts rather than capacity equivalents. Read the separate SL201 assessment and our DoubleStack layout guide before deciding which configuration matches your counter and meal timing.

The SL451's manual lists 120 V, 60 Hz and 1,690 W; SharkNinja lists a one-year limited warranty. The page describes the main material as plastic, while the baskets are nonstick. These are specifications and care claims, not hands-on findings or lab measurements. This model makes the most sense when the probe's Zone 2 use, two independent baskets and extra capacity solve a real planning need. If an integrated probe is not useful, the simpler SL201 avoids paying for an unused feature and still offers separate drawers and stacked racks.

Sources: SharkNinja’s SL451 U.S. product page; SharkNinja’s SL451 product-support record; and the Ninja-authored SL451 Owner’s Guide (document code SL451_IB_MP_Mv3).