We don't get the Corolla Si here in New Zealand as we only got the JDM models (FX-GT), so I've never been able to check one out in person before but judging by online images the seats are identical, just with different fabric. The Si seats look to be identical to the JDM AE101 Corolla/Sprinter GT sedan seats (same seats I have in mine). They use the same style fabric as the JDM AE101 Levin GT Apex seats, although the design is a bit different between the Levin in the Corolla.
So to sum it up, the Si seats are the same as the JDM AE101 Corolla/Sprinter GT sedan, even right down to the same pattern and side bolster support. They're also the same design as the AE101 Corolla FX-GT but the fabric is different.
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