Help with mask

[qash]

Is there a way to make a mask for md5 if i know a part of string but don' t know a length? String is 100-150 letters length. I know ~15 letters.
for example: xxxxxxxKNOW THIS PARTyyyyyy
or it could be:xxx[xx3213xx]yyyyKNOW THIS PARTzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz

[undeath]

String is 100-150 letters length. I know ~15 letters.

lol.

[DanielG]

Sorry, 85-135 length to guess is never going to happen. Ever. It's way too big to guess.

[slyexe]

define your custom character sets with -1 to -4 so we need to create 2 sets of custom charsets. As well we will use increment to limit the search to the 4 to 6 characters at the end.
see below:

Code:

hashcat -m 0 -a 3 -1 Aa1 -i --increment-min 30 --increment-max 32 -2 ?l?u?d?s md5hash.txt ?1?1KNOWNPARTTHATIS24CHARLONG?2?2?2?2?2?2

[slyexe]

Code:

hashcat -m 14600 -a 3 -1 Aa1 -i --increment-min 30 --increment-max 32 -2 ?l?u?d?s header.luks ?1?1mysuper\$ecretPa\$S?2?2?2?2?2?2 --force

Running with --force can cause issues with hashcat and it may not find the password even if it was submitted.