Type USE that does not contain additional insulation designators such as XHHW, RHW, and MTW, is not subjected to the UL vertical flame test and therefore is unsuitable for interior use. The NEC in 338.10 allows up to 6 feet of the USE only to terminate in buildings.
The following is from the UL listing guide for wire and cables
This category covers service entrance cable designated Type SE and Type USE for use in accordance with Article 338 of ANSI/NFPA 70, “National Electrical Code” (NEC).
Service entrance cable, rated 600 V, is Listed in sizes 14 AWG and larger for copper, and 12 AWG and larger for aluminum or copper-clad aluminum. Type SE cable contains Type RHW, RHW-2, XHHW, XHHW-2, THWN or THWN-2 conductors. Type USE cable contains conductors with insulation equivalent to RHW or XHHW. Type USE-2 contains insulation equivalent to RHW-2 or XHHW-2 and is rated 90°C wet or dry. The cable is designated as follows: Type SE — Indicates cable for aboveground installation. Both the individual insulated conductors and the outer jacket or finish of Type SE are suitable for use where exposed to sun. Types USE and USE-2 — Indicates cable for underground installation including direct burial in the earth. Cable in sizes 4/0 AWG and smaller and having all conductors insulated is suitable for all of the underground uses for which Type UF cable is permitted by the NEC. Types USE and USE-2 are not suitable for use in premises or aboveground except to terminate at the service equipment or metering
equipment. Both the insulation and the outer covering, when used, on single and multiconductor Types USE and USE-2, are suitable for use where exposed to sun.
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