free shipping help required

The below is the description for my chocolate bars. Is it possible to have free shipping when they purchase the 6 bars for $18.00 only?

**Solid chocolate bars made with our finest ingredients weighing 50 grams each.

The bars come in white, milk and dark chocolate.

$3.25 each or 6/$18.00**

What shipping modules are you using?

Do you have the bars setup with Attributes or how are you doing the pricing for the single bars or 6 bars?

I am using the 3 cloning method. No particular module.
I have attributes set up for 1 and 6
also attributes for the chocolates in milk, dark and white.

1 for $3.25
6 bars attributed as plus $14.75

Okay you have "some" shipping module ...

Is this a shipping module(s) that is based on products_weight? Or what is the shipping cost based on? Item Count, Weight, Price or something else?

If based on weight, do the attributes hold all the weight? ... meaning is the Product Weight set to 0.00 on the Product itself and the weight is contained on each Attribute?

The shipping is not based on weight. We ship to Canada only.
I have 3 clones.

Normal Shipping
2 Day Shipping
Same Day Shipping within the GTA Only

The above applies to all items bought at the store.

The chocolates bar will be our promo item. How would I add the free shipping for 6 bars if the shipping is not based on weight?

Thanks Ajeh for taking the time to respond. Really appreciate it.

Which shipping module did you clone?

What happens if I buy other things besides the 6 chocolate bars?

Do any of your products use weight?