I've bought lots of little plastic tape measures . . . and they always seem to break.
That's why I searched high and low for this sturdy metal self-retracting tape measure with a key-chain attachment. Now I can take it with me everywhere, or just let it live in my knitting kit.
Note: The tape retracts immediately and does not have a mechanism for staying extended . . . beside you holding it where you want it. Extends to 27" (68.5cm) with an additional inch on the housing for a total of 28" (71cm).