I took some care to ensure that the standard fit would be right for me. I normally find the standard fit of anything going into my ears works (whether it be audio earbuds or various kinds of ear plugs). The one time I tried some large foam earplugs (made by Surgipack from Chemist Warehouse in Australia), they were too big. I have Etymotic earbuds (model HF5) and the standard eartips on those work for my ears. The tips of these earplugs looked identical from the images online. So I was pretty sure that the standard size of these Etymotic plugs would be right for me, but they are slightly too small and do not form a good seal. Comparing these ear plugs side by side with my Etymotic earbuds, the silicon ear tips are identical with the exception of the base where they attach to the main part of the plug/bud. I would not have thought such a slight difference could alter how they fit in the ear canal, but that's the only possible culprit I could find. I haven't been able to try the larger size since they are sold out on Earjobs.
Apart from this sizing issue, the plugs seem good quality. The soft case is very practical - small & comfortable in a trouser pocket. The cord also seems good.