You can buy up to 10 security keys with the offer. If you have multiple account administrators (separate email addresses) for your Cloudflare account, you can buy up to 10 security keys per administrator.

If you represent a larger organization with over 500 employees, you can get 50% off the first year of a 3+ year YubiEnterprise Subscription (no limits on keys for YubiEnterprise Subscription).