Weaver rail which is a Keymod Handrail modified to fit https://www.aliexpress.com/item/FIRE...27424c4dEHfWpA
Luckily found this one that was the correct internal diameter.
Current set up has 1" riser blocks but is still 10mm lower than needed.
Waiting for a UTG Super slim riser and high weaver rings for final set up.