How it works:
MID(A2, 12, 6) returns text which is in A2 starting from 12th positions and 6 characters length;
SEARCH(" cm ", A2) finds the position of the " cm " in A2. +4 gives where next word starts (since " cm " is 4 characters length). Let say it'll be 12.
SEARCH("door", A2) finds the position where "door" starts. Extracting from it previous result minus one we receive the length of the text to extract (let say 6).