Shed kit which chimney size?
If your stove is 5" collar and DEFRA approved (covers most stoves) choose a 5" connection & 5" flue.
If your stove is 5" collar and NOT DEFRA approved choose a 5" connection & 6” flue.
If stove is 6" collar choose a 6" connection and 6” flue.
If your stove is 4" collar and stove is DEFRA-approved choose a 4" connection & 5" flue.