A 50 round loading block for .308 rifle rounds.  Other cases with roughly the same diameter rim fit as well.  Ex: 30-06, 280, 270, 8mm Mauser, 7X57mm, 243, 6mm Remington or any case with a .473" / 12mm case head.  Basically, Many Mauser cartridge or derivative or cartridge based off the 30-06/308 and a bunch more

I have also uploaded a blank sided version of the tray if you intend to use it for other calibers.  

Show in blue in the pictures.

9mm version [https://www.printables.com/model/1255865-9mm-loading-tray](https://www.printables.com/model/1255865-9mm-loading-tray)

38spl/357 version [https://www.printables.com/model/1502119-38-special-357-mag-loading-block](https://www.printables.com/model/1502119-38-special-357-mag-loading-block)

300BLK version [https://www.printables.com/model/1502113-300-blk-loading-tray](https://www.printables.com/model/1502113-300-blk-loading-tray)

308 version [https://www.printables.com/model/1502318-308-loading-tray](https://www.printables.com/model/1502318-308-loading-tray)