Length is the distance from the lowest/ sitting point of the putter head to the end of the grip cap. Identifying the putting posture can help find identify the proper length. Putter that is too long will flatter lie and eye inside-the-line, and short will tend to be more upright lie with eye outside-the-line.
Since the rule banning of Long & Belly Putter from 2016/01/01, lengthened putter are focused on not anchoring against part of the body but to grip-down to equipoise into using the bigger muscles.
ARESO Golf offers the conventional putter from conventional 32”~35” to 37”~41” (equipoised) for different preferences.