This guide bar is referred to as a
12 Inch guide bar because it will provide
a
12 inch cutting depth when used with these Concrete Chainsaws:
12 inch cutting depth when used with these Concrete Chainsaws:

ICS 680ES-GC &
680GC Saws

ICS 613GC
Saws

Cardi & Edco
Electric Saws
Guide Bar P/N 71395 - Referred to as a "12 Inch Guide Bar"

Overall Length:
17.5 Inches (44.5cm) 
Buy any TWO 12" TwinMAX Chains
and get THIS $159.95 Guide Bar FREE
Includes 2 Chains and This Bar FREE
TwinMAX-29
General purpose
ComboPack:
$659.90
General purpose
ComboPack:
TwinMAX-29 Plus
Reinforced concrete
Combo Pack:
$859.90
Reinforced concrete
Combo Pack:
TwinMAX-29 Abrasive
Soft abrasive material
Combo Pack:
$799.90
Soft abrasive material
Combo Pack:
Chain Tensioning
Tip Sheet
Tip Sheet
Concrete Cutting
Tip Sheet
Tip Sheet
Chain Life
Tip Sheet
Tip Sheet
This ICS video shows proper chain tensioning.
Why is the overall length of my guidebar different
from the descriptive length of my guide bar?
from the descriptive length of my guide bar?

Overall Length
A guide bar that is called a 12" bar on one saw may have a different overall length from a guide bar on a different saw. This is because the drive sprocket on different powerheads are positioned at different distances from front of the saws.

Descriptive (Called) Length
ICS Describes their guide bars by how deep the saw is able to cut into a concrete wall. A 12" guide bar cuts 12" into a concrete wall. The saw is able to cut 12" because the bar extends 12" out from the saw powerhead. That is why these two lengths are different.
It is best to use the overall length when your not sure of which guide bar to buy. The overall length will always remain a constant.
However, as your chain stretches during normal use, you'll use the chain tensioner to extend the guide bar, and it is therefore a less reliable measurement.
However, as your chain stretches during normal use, you'll use the chain tensioner to extend the guide bar, and it is therefore a less reliable measurement.