Why don't you list "additional temperature ratings" with Reactor Series Liners?

Because there is standardized test for measuring the warmth added by a liner, any “temperature rating” would only be an educated  guess.
 

Sea to Summit tests sleeping bags to the ISO standard and sleeping mats to the ASTM standard, but no such protocol exists for liners. Testing a liner inside a sleeping bag during ISO evaluation wouldn’t solve this – this would only produce results specific to that one bag/pad combination and still wouldn't be tested according to an accepted protocol.
 

There are a huge number of variables that impact the thermal boost you can expect from a liner. Beyond the obvious environmental conditions, two major factors play a role:

• Sleeping bag design: Some bags are simply better at retaining warmth than others. Features such as hoods, draft collars, draft tubes, and shaped footboxes can make a big difference. A live, moving sleeper also creates opportunities for heat to escape that a static test manikin cannot replicate – and this heat loss is not reflected in the ISO or EN temperature ratings.
• Sleeping pad insulation: Some pads hold warmth far more effectively than others. Even with the same listed R-Value, internal air movement in a pad can dissipate heat, reducing its real-world performance.

With a high-performance sleeping bag that minimizes heat loss and a well-insulating pad, a Reactor liner might realistically add 7–10°F (4–6°C). In contrast, paired with a bag that loses warmth easily and a pad that dissipates heat, the very same liner may contribute only 3°F (2°C).

This wide variance – between 3°F and 10°F – is why quoting a fixed “additional temperature rating” is misleading. The real-world benefit depends heavily on the specific combination of your sleep system and environment.

Learn more in our blog post: Adding Warmth with a Liner