Depends on the manufacturer/model
It sounds like 29/29.5 shell size, but BLS is not a good indicator of the actual length inside the boot, only the sole - it often varies across different models even within the same brand
e.g.
Nordica 09 29/29.5 shells v BSL
Gran Tour - 330mm
Speedmachine/Beast/Sportmachine - 335mm
Gran Sport - 333mm