.{6,30}
Dot (.) matches any character except line breaks (\n), unless you specify RegexOptions.Singleline in the Regex constructor, in which case it matches every single character. And it always matches carriage return (\r), just in case you were wondering. And 6,30 is the range of characters to match using the match expression to the left of the range (in the above case, that would be dot). So, the above expression matches between 6 and 30 characters (of any type, except for \n depending on how you construct the Regex), inclusive.