Thank you for your question.
The free fitting kit consists of:
1M or 500mm stove pipe in matt black.
1M x 500mm 2mm stainless steel register plate (blank - cut holes to size)
Choose these when ordering if required and a heat resistant stove glove.
The optional flue liner pack consists of a flue adaptor which connects the stove pipe to the flexible flue liner, Dura Flue flexible flue liner (this is 6" in diameter and 316 Grade) cut to the required length and a 6" pot hanger rain cap this supports the flue liner from the top of the chimney and also acts as a bird guard and rain cap. The 316 grade flue liner has a 15 year guarantee, if you require an improved grade we also supply Dura Flue 904 grade flue liner (30year guarantee) which can be found here - https://www.directstoves.com/catalogsearch/result/?cat=0&q=904
Hope this helps?