The silicone rubber straps are recommended for the lower StarFish clamp. They grip glassware, and are very durable. The silicone clamps have a handle for lifting glassware away from the heat.
The Velcro straps are recommended for the upper clamp. They are designed to not grip glassware tightly, allowing condensers to slide through the straps when glassware is lifted, whilst still offering some support. Please note the Velcro straps are not suitable for suspending unsupported glassware. The Velcro can be weakened by exposure to high temperatures, chemical vapours or sunlight. Velcro straps and pads are consumable items that should be replaced as required.