Mountain Eagle spoke while pulling out an AK74 equipped with a modernized Zenit kit from his large bag...
In the AK modification community, the Zenit kit is probably the most famous.
It involves replacing the upper receiver and handguard to circumvent some issues with the AK, although it makes the gun slightly heavier, but compared to the gains in appearance and performance, that bit of extra weight is nothing to worry about.
Most of the mechanisms in the AK series rifles are concentrated in the lower receiver. Originally, to save costs and reduce weight, the upper receivers of AK series rifles were designed to be very thin and light...
For most people, the most prominent issue with this design is the inability to mount accessories.
