Norway will provide Ukraine with missiles to use by the IRIS-T SLS (Surface-Launched Short-range) anti-aircraft systems. The Norwegian government announced the transfer of spare missiles and added that new ones, "matching those donated to Ukraine," would be procured as replacements.
For a reminder, the first IRIS-T SLS systems were supplied earlier by Germany this month, and Sweden committed to donating more in February 2023 with deliveries coming through Germany. But the interesting part is, Norway itself doesn't have any SLS systems in service yet sends missiles, so the reasonable question is where the materiel comes from.
Read more: Officially: Third Donor of F-16s to Ukraine is Norway

The only type of air defense system Norway has in service is NASAMS III: two battalions in the Air Force and an unspecified number of launchers in the ground forces, according to The Military Balance 2023.
However, there still may be some IRIS-T missiles left in stock from the times the Norwegian Air Force used the F-16, decommissioned in 2021.
The ability to deploy German IRIS-T from F-16 was a feature unique to the Norwegian fighters specifically. In the context of Norway's pledged donation of F-16 to Ukraine, this factor should be accounted for, as these missiles will come in handy, not for the SLS launchers alone.

Provided that Ukraine is planning to upgrade its fleet with a variety of Western aircraft, the issue of how to provide sufficient quantities of weapons carried by different types of fighters becomes all the more important. Here, a dual-use IRIS-T missile that can be deployed from both an air platform and a surface launcher becomes a must-have for the Ukrainian military.
First, we had an example of the AIM-120 air-to-air missile which can be used by both F-16 and JAS 39 Gripen fighters, as well as by NASAMS on-ground launcher. Now a similar story with the IRIS-T.

The only question left is, why does Norway need to replace its IRIS-T stocks after the donation to Ukraine? The thing is, the Norwegian Ministry of Defense for a while has been considering acquiring a new kind of ACSV G5 vehicle equipped with an air defense launcher. The vehicle is in development, it will be able to deploy IRIS-T and potentially AIM-9X missiles, too. Apparently, the government is already concerned with filling the arsenal with ammunition to this asset.

Read more: The Biggest Mystery of the Latest Aid Package From Germany: Laser Targeting for IRIS-T SLM