We will never use gels in our Memory Foam (Visco Elastic), they restrict air flow and can make you sleep hotter. Airflow is the key to cool sleep.
We will never use waterproof membranes. We all sweat to some extent, the average is 200 millilitres per night, when we sleep and the waterproof membranes trap moisture near your body. This is not only uncomfortable but can lead to mould forming on the outer cover. Moisture should pass through the mattress as quickly as possible. Waterproof membranes also restrict air flow.
We will never use springs, this is old technology. Springs cannot deliver the comfort that modern material can now achieve. Springs also make the mattress heavy and hard to lift when making the bed.