The differences are the size of the bottle and the filter life. The 75cl (black) bottles include a larger filter that is effective for 200 litres (3 months of constant use) whereas the smaller (clear) 50cl GO! bottles have a smaller filter that is effective for 130 litres (2 months of constant use). There is NO difference with the filter technology – they both eliminate well in excess of 99.9% of all microbiological contaminants from any non-saltwater source.
