These were from NVScopes and I believe no longer available.
They were advertised as 8 round magazines, but I have only ever used them with 5 HMR rounds as that is what I tip out of the ammo box! I have not tested with WMR.
Advertised as working for both 64 and 54 series actions, though I have only used in my 64 actioned 1517.
Good used condition.
Two available. £40 each.
Also for sale elsewhere.