The top companies of STI Index are SGX:D05, SGX:O39, and SGX:U11 — they can boast market cap of 82.91 B SGD, 51.64 B SGD, and 40.62 B SGD accordingly.
The highest-priced instruments on STI Index are SGX:J36, SGX:D05, and SGX:U11 — they'll cost you 38.88 SGD, 38.75 SGD, and 32.10 SGD accordingly.
The champion of STI Index is SGX:BS6 — it's gained 74.48% over the year.
The weakest component of STI Index is SGX:C09 — it's lost −17.92% over the year.
STI Index is just a number that lets you track performance of the instruments comprising the index, so you can't invest in it directly. But you can buy STI Index futures or funds or invest in its components.