When choosing the right anti-siphon device for your vehicle or fleet, it is important to consider:

1. Installation method - there are many different installation methods, some with grub (set) screws, fixing with one-way screws, rivets, glue, bending tabs, spring tabs, etc. You might want to avoid the ones with screws or rivets, as they require drilling the fuel tank, which can affect tank sealing. They can be found on the cheapest products. Rivets are also quite easy to remove. Glue fitting is inconsistent and can be messy. Other methods' ease and security depend on their design for example large bending tabs can leave big holes in the body of an anti-siphon, which defeats the purpose of an ASD.

2. Security consists of ASD strength - how well it resists break damage, size of the holes - whether they offer protection from smaller hoses, reliable fitting - whether it is possible to remove the whole ASD. Strength of ASD is important, but it's a matter of balance, as there is nothing unbreakable and it should be strong enough to make theft difficult, noisy and time consuming. This will deter most of the thieves, while a well-prepared thief or gang will find their way to the fuel anyway. The size of the holes should not exceed 6 mm; with larger holes, smaller hoses can be used to siphon fuel. In certain conditions, slow speed is acceptable. Fitting has to be secure and should not allow removal of the whole device.

3. Protection from skimming. Skimming is the term used to describe siphoning the top layer of fuel from an over-filled fuel tank. This layer can be reached from inside an ASD and the longer the ASD is, the deeper it dips into the tank, the more fuel can be skimmed. As a general rule, the shortest device will work the best; however, there are other methods to stop skimming, e.g. a shut-off valve (float) which will close the ASD's chamber in a full tank. The idea is great, but in some designs, it can be hacked - a valve can be depressed or even jammed for easy siphoning. In such cases, an inspection will not show anything suspicious and the ASD will be considered secure.

4. Refill speed varies greatly around the world. For example, diesel pumps in Europe are mostly limited to 30-40 litres per minute to avoid filling issues with a vast range of cars, vans, light trucks etc. HGV fuel stations have high-speed pumps - up to 120 l/min or even up to 150 l/min. High refilling speed is important to reduce time spent off-road, especially for high volume fuel tanks on long haul trucks. Any ASD is an obstacle for fuel and at high flow speeds it can bounce back, splashing out badly and also cutting off a fuel nozzle. To dissipate fuel at this flow rate, the construction of an ASD must be more than just some drilled holes in a cylindrical basket. To improve the flow, some ASDs have longer bodies, which allow a lot more skimming. Or they will direct a fuel nozzle in a specific way or limit acceptable nozzle types and sizes, which might make a simple refill problematic and inconvenient. A shut-off valve on some ASDs doesn't help as well - when fuel reaches the valve and starts pushing it up, the filling speed will drop down a lot and will require driver's attention and more time to finish it.

5. Corrosion resistance. The most common ASD materials are aluminium alloys, steel or plastic. Aluminium and plastic have very good corrosion resistance, but steel has to be coated, and some cheap coatings don't last long; for example, an external ASD with a basic zinc coating will definitely rust in a couple of years in wet conditions, especially in a marine climate.

6. Compatibility with existing fuel caps is another thing to look at. Most anti-siphons can work with OEM fuel caps, but some require a custom one, which could come at extra expense or be inconvenient to use.