Model identity
Chefman RJ21 vs RJ21-IN: two different burner types
Similar codes, different cooking hardware
Chefman lists two short model codes in its Electric Cooktops document library: RJ21 and RJ21-IN. The suffix changes the appliance category. The separate U.S. RJ21 guide identifies an electric single burner with a heating element and burner plate. RJ21-IN's exact-cover U.S. guide identifies a Precision Induction Cooktop. Do not treat the suffix as a harmless spelling variation, infer induction operation for an RJ21, or transfer the RJ21-IN controls to it.
What the RJ21-IN guide actually documents
For the RJ21-IN, the exact manual describes one induction zone, eight discrete power labels from 300 to 1,800 watts, and eight separate TEMP choices from 140 to 465°F. The values are unevenly spaced, and the manual does not identify the TEMP control as a food probe or a calibrated pan-temperature measurement. Its maximum countdown is 2 hours 59 minutes. It says to use an induction-compatible magnetic-base pan no larger than 12 inches, but it does not specify a minimum magnetic base or the cooktop's voltage and amperage.
Those facts belong only to RJ21-IN. RJ21's electric-burner manual describes burner plates and a heating element instead of induction coils. Since cooktop technologies demand different pan compatibility and operating assumptions, a seller's brief title is not enough to identify what is being offered.
How to check an existing unit or offer
Read the rating label on the appliance and compare its complete code—including the “-IN” suffix—with the guide supplied for that exact unit. For a used RJ21-IN, verify the unit's condition, cord and glass surface, and consult its rating label for electrical requirements not stated in the guide. The manual's three-year limited-warranty description for the original U.S. retail consumer does not establish that a second-hand unit remains covered. For either code, don't assume cookware will work until the exact manual's heating type and pan instructions are clear.
The RJ21-IN review is available only among earlier models, because the manufacturer support library still provides its manual but the current product feed did not return an exact current product entry. This is not proof that no seller has stock. The plain RJ21 may be useful to research separately if it is your exact model, but its exact guide identifies it as an electric single burner rather than a portable induction recommendation.