The kit includes O rings for scuba cylinders in both common sizes, in standard and green viton for enriched air (Nitrox); DIN regulators, the ones that go on the end of the hoses for BCD's, regulators and gauges (including the large bore style), plus those little fiddly ones that fit on the swivel pin that stop your gauges from bubbling. A this in a sectioned mini-case that will fit in the corner of any dive bag. A great value kit.
What more could you want from a spares kit? OK, free postage and packing.