27 CFR §40.135

Where the amount of any bond is no longer sufficient under the provisions of § 40.133 or § 40.134, the manufacturer shall immediately file a strengthening bond in an appropriate amount with the same surety as that on the bond already in effect, unless a superseding bond is filed pursuant to § 40.136. Strengthening bonds will not be approved where any notation is made thereon which is intended, or which may be construed, as a release of any former bond, or as limiting the amount of either bond to less than its full amount.