Most modern films are pre-hardened, only a few are softer emulsions. Manufacturers don't recommend a hardening fixer these deays except for extremes likle high process tempertaures.

As Matt says Hypam is a non hardening fixer buffered to be usewd with a hardener if required. In nearly 40 years of using Hypam I've never seen the hardener on a dealers shelf as almost no-one uses it. Ilfotd Rapid Fixer is very similar but with a much lower level of buffering which makes it cheaper to produce. The buffering has no effects on the fixing but the pH must be kept more stable (around pH 5.2 - 5.4 for a hardener to work/

Ian