**Seac** is **highly esteemed for its rubber bands line** for sling spearguns. With the 2023 catalog the offer is very complete. The range is made of the **Tripower, the Progressive Power Red, the Progressive Power Blue, the Anthracite Flex and the Power Flex**. Let’s see the details of each type of rubber band.

**Materials and design **

The **5 different types of Seac rubber bands** are made of **different compounds of natural latex**. They vary in external diameter, while all of them have an **internal hole** of the same diameter equal to **3 mm**. The **Tripower **and the **Anthracite Flex**, as visible by the colour, have a **different natural latex internal layer**. All the bands have an **external layer** of material to **protect **the natural latex from **atmospheric agents and sun rays**.

**Diameters and versions**

Each rubber band type is offered in various diameters and “versions”. All of them are available in lengths which can be cut at ones’ liking and needs. The **Tripower **is sold in the diameters of **14.5 and 16 mm**, and also as circular band with Dyneema wishbone, **Tripower Dyneema**, and classic straight pair with plugs, the **Tripower Dual**. The **Anthracite Flex **is available in 3 diameters: **14.5, 16 and 17.5 mm**. A **circular **version and a classic double straight, the **Dual**, both with **plugs**, are available.

The **Progressive Power Blue** is offered in the diameters **14.5, 16 and 17.5 mm**, and with **circular **band with **plugs**, or classic straight pair with **plugs **(**Dual**). The **Progressive Power Red** is available in the same diameters as the Power Blue, but has only the classic straight pair (**Dual**) with plugs and no circular. Finally, the **Power Flex** has a line of **4 different diameters: 14.5, 16, 17.5 and 19.5 mm**, and only to measure.

**Elongation coefficient**

Key to understand the length to be used on every sling speargun is the **elongation coefficient indicated by Seac**. Such value suggests the **optimal elongation of a rubber band** so that it works in the most efficient way. Below such value the rubber band does not utilize all its power. Above, it deteriorates losing elasticity in time and also the additional effort to stretch the elastic band does not lead to noticeable increase in power, but potentially loss.

In the Seac rubber bands line the lowest elongation coefficient is equal to **3.3 for the Power Flex and the Progressive Power Blue.** **3.4 is the value of the Tripower and the Progressive Power Red**. Finally, **3.5 is the elongation coefficient of the Anthracite Flex.**

What does this mean? Let’s make an example: we have a circular Tripower band of 60 cm on a 90 cm sling speargun. To load the speargun we will stretch the elastic band to 90 cm (indicatively) on each side. So taking into account only half of the rubber band, 30 cm will be stretched to 90 cm. This will mean that 90/30 = 3 (or 300%). So the elastic band is stretched 3 times its length. The elongation is not enough. To reach the elongation of 3.4 we will need to have a circular elastic band of 90/3.4 = 26.5 cm per side, so total 53 cm. Clear?

Actually, to be **more precise**, we must not consider the nominal length of the speargun. We should instead take into account the measure of the distance from the muzzle to the notch or shark fin where the wishbone will be connected to the shaft. Also, we should eliminate the length of the wishbone in our calculations.

So, if the distance measured is 92 cm as on the **Seac Fire 90**, that we have also **tested**, the length of the Tripower circular band should be 27 cm times 2. But, since the Dyneema wishbone measured entirely, meaning also the part inside the elastic band, is 7 cm long per side, the useful length is not 92, but 85 cm. The new calculation will be 85/3.4 = 25 cm, for total 50 cm of circular Tripower elastic band. This is, in fact, exactly the length of the circular band mounted standard by Seac on the Fire 90.

**Mechanical characteristics and performance**

The choice of rubber bands for sling spearguns is always quite complex. So, we have asked Seac a clear indication of the **performance and behavior **of each of their types of rubbers. The indications we have been looking for are: **Power, Reactivity, Progression and Durability**. On a scale of maximum 5, below we you can easily read the values given by Seac. It is evident how the **Seac Tripower excels in each parameter**, but is also **by far the most expensive**. We will anyway test with Apneapassion international Test Team the various rubber bands to verify the final behaviour.

Tripower Progressive Power Blue Progressive Power Red Anthracite Flex Power Flex Power ***** **** **** **** *** Reactivity ***** **** **** ***** **** Progression ***** ***** ***** **** **** Durability ***** ***** ***** ***** *****