The extra O-ring which comes with the single fitting BP-EML14 is for the tube which OD is a little smaller. But since most of the tubing is stander OD14mm, so mostly the O-ring is of no use. BP-EML14-6P is the 6 pcs kit with a special unit price. So there is no extra O-ring in it. If you need the extra smaller O-ring, please send an email to the following address, we will send a quotation to you. Thank you.