How to set the item with different variation?

There two methods for product with different variations such as small, regular, large 

1st method: 

When creating of products, the barcode key in XXXX-1 for 1st product and XXXX-2 for 2nd product. 

Eg. 1001-1 and 1001-2 

This would meant that they are variation of same product 

2nd method: 

Using of specification 

Go to product information and edit the products. 

Activate other variations 

The specifications is used to differentiate the product. 

Key in the price, cost price and barcode no. of the variants.

This will link the product to be of different specifications