Is this lock really rustproof?

The body and shackle are stainless steel with a chrome finish, which resists rust and corrosion in rain and humidity. Stainless steel can still stain or pit over years of salt air or constant wetting, so a quick dry and occasional oil in the keyway helps.

What can a 30mm short-shackle padlock secure?

It fits hasps, chains and handles with a small opening: shed doors, gates, lockers, cabinets and storage units. The short shackle is harder to cut, but the small body means it is not the right lock for expensive equipment or a main entry door.

How many keys come with it?

Four keys are included, so you can keep spares or give one to a family member or coworker. Replacement keys are not standard, so keep the spares safe.

Will it work outdoors in winter?

The stainless body handles cold and wet weather. The keyway is the weak point: moisture and grit can freeze or jam it, so flush it with a graphite or silicone lubricant before winter.

Is it as secure as a long-shackle padlock?

It is harder to cut because there is less shackle to reach with bolt cutters. It is less flexible, though: it will not fit around thick chains or wide hasps the way a long shackle does.