Verify the correction range claim

A stabilizer is only useful to the extent of its correction range and its accuracy at the extremes of that range. Ask for the figure at the worst input voltage at your site, not at nominal.

Verify the rating basis

Ratings are quoted in kVA. Ask what the unit delivers in kW at the power factor of your load, and what it does when a motor starts.

Verify serviceability

A servo regulator has moving parts. Ask who services it locally, how quickly a servo motor or control board can be replaced, and whether spares are held.

Verify the installation scope

Cable sizing, protection, bypass arrangement and commissioning are part of the job, not extras. Establish who provides them.