Vertical blinds are now available to purchase in 127mm slat widths or 5″ wide fabric drops as they are also commonly named.
The narrow slats are called 89mm louvres as they are just under 90mm wide, whereas 127mm are approximately 13 centimetres across. The reason why many manufacturers tend to shy away from supplying the wider louvres is simply because this would mean the supplier would have to make two different types of top rails for the slats to attach to resulting in a higher overall production cost.
Narrow vertical blind slats will have more pieces of fabric on the rail than a traditional wide slat system would because of the sheer amount of material needed to cover the whole window.
The more louvers that are attached to the runner of your top rail the more parts you will need, parts are located inside the fabric at the bottom of the fabric and are called bottom weights and chains. The chain is used to keep the slats from drifting apart and becoming very untidy.