Blade width matters as much as length, because it decides how far the tape will stand out unsupported. A 16mm blade folds within a metre or so. A 32mm blade stands out several metres, which is what lets one person measure across a room. That figure is not usually printed, but blade width is, and the two go together.
Length and width move together for that reason. A 3m tape at 16mm is a pocket tape for close work. A 10m tape at 32mm is a site tape. Buying a long tape on a narrow blade gives length that cannot be used without a second person holding the end. Reading both figures together is what avoids a tape that measures further than it will reach unaided.
Lock type changes how the tape is read. A manual lock holds the blade when the button is pressed. An auto lock holds by default and releases when the button is held, which suits repeated measurements where the blade would otherwise retract between them. Both lock types are held across the same lengths, so the length does not restrict the choice.
Long distances need a different tape entirely. Fibreglass surveyors tapes at 50m and 100m are wound on an open reel and laid on the ground rather than standing out, since no steel blade will span that. Send the work to 07754288583 on WhatsApp. Abracs hold 5m and 8m tapes alongside the Draper and Redline bodies. Fibreglass does not stretch under tension the way a fabric tape does, which keeps the reading honest.