This kit contains pre-measured ingredients; all you need to do it mix and make a choice of 30 fragrances and a mix of colours to choose from. The box is able to fit via most domestic mail boxes, siding ease of delivery. 
You will be able to make approx 3 standard sized bath bombs in the kit. It also makes a lot of fun. Full instructions with step-by-step images to follow.
The mould (not included) is an additional extra, but you can use your own or order one to come with your kit.