The step height on the box is measured on a staircase. At a doorway threshold, the robot clears about half of it

Robot vacuums with lifting chassis are sold on one number: how high an obstacle they climb. Two manufacturers' own specification tables show that the advertised figure is measured on a double step — two edges in a row — and that a single threshold, the thing actually found in a doorway, has a separate and much lower limit. Dreame's X50 Ultra, added to our catalogue today, advertises 60 mm. The company's own table qualifies that as a two-step climb, and its footnote adds a condition: the gap between the two steps has to be wider than 40 mm. For a single vertical obstacle Dreame states 42 mm. The 2026 successor, the X60 Ultra, repeats the pattern with a wider spread: 88 mm on a double step, 45 mm on a single one. Ecovacs describes its DEEBOT X12 OmniCyclone the same way, in inches: single thresholds up to 0.94 in (24 mm), continuous double steps up to 1.57 in (40 mm). In all three cases the headline number is between 1.4 and 2 times the single-threshold figure. The distinction is not a trick of wording — a chassis that lifts its front wheels onto a first edge can use that edge to lever the rear wheels onto a second one, which is why a staircase-like pair is easier than one tall lip. It is, however, the wrong number for the buyer's question. Doorway thresholds, balcony rails and shower kerbs are single obstacles. Read against the smaller figure, the segment's leaders clear 24 to 45 mm, not 40 to 88 mm. All figures in this note come from the manufacturers' own specification tables and footnotes, and all are described by them as in-house laboratory results.