This Slocable brand MC4 fuse is intended for off-grid ELV PV arrays of 3 or more strings.
If you require both poles to be fused, then buy 2 and install one in both the +ive and –ive wires. You must not open them under load, so ensure that after the strings are combined that a correctly rated DC switch is used before the PCE (power conversion equipment) so that the arrays can be turned off.
Read more detail in this topic here.
Note: if wiring your own system in NZ, you can do so for voltages up to 120 VDC (ELV) if you have suitable knowledge and experience. For LV systems (>120 VDC) this is prescribed electrical work and it must be done by a licenced electrician.