Approximate inner size: ca. 3.7 cm x 15.5 cm x 8.3 cm
What can you put in that space:
1. Road bike inner tyre (23-622) + tyre repair kit with some tyre levers + minitool or a bunch of inner hex keys + mini chain tool (such as Park tool's CT-5).
2. Touring bike inner tyre ca. 35-622 + very small tyre repair kit and small tyre levers. No room for anything else!
A Schwalbe SV17 inner tyre for 28-622 up to 40-635 is ca. 10.5cm x 6.5cm x 3.2cm rolled up as it comes from the factory and squeezed together for minimum volume. So not much room left...