ctypebmt.zip is a release file of the Minecraft resource pack BMT C-type In Voxel for Immersive Railroading, made for Minecraft 1.12.2. It was published on April 23, 2021 and is 0.3 MB in size. For the full description, screenshots and every other version, visit the BMT C-type In Voxel for Immersive Railroading resource pack page.
How to install: Put the .zip into .minecraft/resourcepacks (do not extract it) and enable it under Options → Resource Packs.