Its SIM sticker can be easily pasted on the chip of a SIM card, but it feels slightly thicker than Interfone's SIM sticker.

The Slimduet SIM sticker, which costs US$13 (S$17)to ship, comes with sandpaper for filing down the plastic on the SIM card host should users find it hard to slide it into the phone after adding the sticker.

Taisys also sells a regular Slimduet SIM card - a physical plastic - for mobile users who have Android phones with dual-SIM card slots.

Users must register the SIM card sticker or the regular Slimduet SIM card via the Slimduet app with their Singapore phone number and e-mail address to start using the service.

Slimduet lets travellers download virtual prepaid SIM cards on their phones by reselling the actual prepaid plans of some 200 telcos around the world.

The rates are the same as what users would get at overseas prepaid SIM counters - just minus the queueing. The other benefit is that users get their overseas numbers prior to leaving their home country, allowing them to notify their contacts ahead of their travels.

ST PHOTO: IRENE THAM

The Slimduet SIM can store up to 32 previously purchased numbers. As long as the overseas prepaid SIM cards bought have not expired, travellers can keep the number and top up its value for the next visit.

Irene Tham