After the zip, the seals are the next important part of a drysuit. They create a seal between your neck, wrists (and possibly your ankles) and the suit, preventing water getting inside. Why not order a set of spare drysuit seals that can be fitted yourself, or make up a dry suit repair kit for those longer dive trips.
For the neck and wrist seals there are three options, either Silicone, Latex or Neoprene. Seals are best considered as consumables and are likley to require replacing during the life of the dry suit.
Latex Drysuit Seals
Latex Seals offer the most waterproof seal when compared to neoprene, especially for the neck. Latex seals are cheap and simple. If you know your size it's pretty easy to swap them over yourself. Latex seals are soft and give a reliable seal, they come in a few thicknesses, the thicker they are the tougher they are but thinner ones give a softer seal so you don't loose circulation.
Latex stretches over time so your neck and cuffs feel really tight when you first fit them, to the point of cutting off circulation, so you have to stretch them over a cylinder for a few hours so they're more comfortable. You can cut them down to make the seal larger but if you do it too early and they continue to stretch you'll end up with a loose seal that leaks.
Silicone Drysuit Seals
Silicone seals have all of the best features of latex with very few of the drawbacks. Silicone is thin and flexible so you can don and doff your suit more comfortably. It's hypoallergenic so people who suffer from latex allergies are fine to use silicone seals. Silicone is more flexible and stretchy than latex, but some find them to be more fragile than similar latex seals.
Because very little sticks to silicone once it's set you need to use a ring system around your wrists and neck. While they first looked uncomfortable, the rings are now comfortable and practical thanks to newer more flexible and ergonomic designs.
Silicone seals are sandwiched between a hard internal ring and a softer external ring glued to your drysuit so you can change broken seals in minutes not days. Carrying spare seals in your bag is easy and can save a dive even when you're off shore on a boat as you only need a simple tool to swap seals over.
More and more divers are using dryglove systems that fit almost any drysuit, which is an added benefit of rings. The design of some neck seals adds a bellow so you can move your head around without breaking the seal. Silicone can also come in a range of shapes and colours instead of standard black. Bright colours are a great way to personalise your suit and stand out of the crowd.
Neoprene Drysuit Seals
Neoprene seals are warmer to wear compared to latex seals and are sometimes considered more comfortable. They also have a tendancy to last longer. Neoprene is good at spreading the pressure over a wide area so you don't end up with Latex love bites, but getting the right size can be tricky.
Neoprene does stretch, but nowhere near as much as Latex or Silicone so they can be harder to put on and the glideskin sticks to your skin so you need to lubricate to get them on. The glideskin is great at sealing against your skin but is quite fragile so you have to be careful pulling it on or it can tear. Ripped neoprene cuffs can be easily fixed if the rip isn't too catastrophic.