Modifiable antonyms

What is the opposite word for Modifiable?

• unmodifiable
• rigid

  able and usually willing to change
• inflexible

  able and usually willing to change
• stiff

  able and usually willing to change
• intractable

  able and usually willing to change
• nonconforming

  able and usually willing to change
• unadaptable
• nonmodifiable
• immutable

  nonmodifiable