The original Jagdpanzer IV tank destroyer was based upon the Panzer IV vehicle and used extensive sloped armor with the 48-caliber 7.5cm gun that had already proven its worth on other vehicles. In January 1944, it was decided to upgrade the Jagdpanzer IV, with the powerful 70-caliber 7.5cm anti-tank gun installed in place of the original 48-caliber weapon.
I would highly recommend the new release Tamiya kits. Older Tamiya kits are ok, but they are a product of there time and do not compare to modern kits. The newer Tamiya kits are fully up to modern standards and you will pay a lot more for a competitors kit such as Dragon models (and they have there issues). Just check the release (new tooling) date of the kit and if it is from the last couple of years buy with confidence. The older Tamiya kits are fine for new starters to modelling and can be bought quite cheaply but this kit is well worth the extra cost.