Configure options that don't increase weight

Sirs,

How do I add an option to a product so that it doesn't increase the weight or the cost of shipping? I have added an option that has no weight to it, yet when I add it to in item, it doubles the shipping cost.

If I leave the weight and dimension out, then I get an error message.

Hi,

If you don't put a weight in the option product, it won't be taken into account for shipping methods.

Well I did just what you say, and I get the error message that is in the attached image. If I add any weight at all, then the shipping gets doubled. Even if I add 6 oz.

I think I found the answer. The option that says group products was set to no. That appears to be the fix.