The new rail system had to be STANAG & SOPMOD Block II - compliant. It had to permit all factory functions of the
rifle (fieldstrip, GL) & accept all
SOPMOD B2 attachments.

It had to withstand temperatures of -40°C and +100°C, 345 rounds of fully automatic fire and the recoil of at least 400 shots from the GP-34 underbarrel grenade launcher or similar without any maintenance.

It had to weigh no more than 300g (10% of the rifle's weight or less) and to be drop safe from 2m.