My nephew, Chong, gave me a bag of this fruit which I have seen at Satok market before. We bought some then but it did not taste very nice - possibly not fully ripened. So I was a bit wary but my nephew told me that they are really sweet - the fruit is marketed as Australian Longans but it is actually Fijian Longan (Pometia pinnata) and known locally as kasai. Apparently, Fijian longan is a fast growing tree reaching a height of 60-90 feet (18-27 m). So it is certainly not a tree for the home garden!
The shell is pretty tough and needs to be cracked with a pestle or small hammer.
The fruits do look like longan and they taste like longan - sweet though not as sweet or as juicy as longan. It is a nice fruit and we polished off the whole bag in a few minutes :-)
The pictures did not come out very nice but no re-takes of the fruits as we have finished off the lot! :-)