It depends on how tight the GM wants to be.
All it says is "one type of clustering weapon, be it a missile or rocket launcher, an ultra or rotary autocannon, or an LB-X style weapon".
For our campaign, the DM just listed it as "Sandblaster: Missiles", and we have a slightly modified Steiner Archer in the group (LRMs and SRMs). The pilot who had that ability has not had any reason to use their SRMs, yet, so it never came up, and she started with a Valkyrie.
So if the DM chooses it works for all Missiles, then it will work with SRMs, LRMs, MRMs, NLRMs, ELRMs, ATMs, and iATMs.