Find the family.
Then the exact fit.

1 kV–1,200 kV; hundreds to thousands of amperes; porcelain/composite, OIP/RIP/RIS and dry variants

Distribution/network transformers through 1,300 MVA/EHV units; 200–6,000+ A through-current; diverter/vacuum/resistor/reactor types

Motor-drive units for specific OLTC/DETC; 24–250 Vdc and 110–690 Vac controls; local/remote/monitoring

Small transformer panels through multi-bank power-transformer coolers; natural/forced oil; custom flange and heat duty

About 100 mm to >1.5 m diameter; tens of watts to tens of kW; AC/DC, low-noise and offshore variants

About 1–1,000+ m³/h and 0.1–100 kW; axial/centrifugal, sealed transformer-oil service

Tens of kW to multi-MW heat duty; oil-air and oil-water; plate, finned and shell/tube

Tens of litres to tens of thousands of litres; open, bladder and diaphragm types

Pipe sizes about DN25–DN100+; one/two-float; gas collection, alarm/trip and monitoring outputs

About DN25–DN250+; opening pressures and discharge capacity matched to tank; mechanical/electrical alarm

Drums/IBCs/bulk; mineral inhibited/uninhibited; dielectric classes and reclaimed oil

Drums/IBCs/bulk; distribution through EHV application grades; fire point and oxidation packages vary

1–16+ RTD/analogue channels; winding hot-spot simulation; local gauge through digital monitoring

Oil ppm/relative saturation and paper moisture estimation; portable or online; single/multi-sensor

Single hydrogen sensor through 9+ gas chromatographic monitors; portable, online and fleet-connected

Distribution cans through tanks for 1,300 MVA units; welded/corrugated; transport-separated designs

Small EI/toroidal cores through hundreds-of-tonne GOES cores; step-lap, wound and amorphous

Copper/aluminium; foil, layer, disc, helical and continuously transposed conductor; kVA through 1,300 MVA