Note: 10g through 6g can be difficult to work with. You will probably need to exercise extreme patience, as it can be quite time consuming to get them in.
These are thin-walled silicone eyelets that make your piercing look like a round, open hole. They should not be used to stretch with, as they may be unable to keep a freshly stretched piercing at the new size. The flares on these are not like regular plugs where they come out and around your lobe--they are extremely small flares that barely come out of your piercing.
Jewelry is measured through a gauge system (see chart below). The higher the gauge number the smaller the wire is. A standard "earring" is usually 20 gauge. Jewelry gauges/sizes can vary between manufacturers. There is no universal regulation on companies to make a standard size in body jewelry. A big part of this is that some jewelry is made overseas and measured in millimeters. And in the USA jewelry is measured in inches/gauges. So many times jewelry can be anywhere from .5mm to 1mm different.