Whatever outdoorsmanship you enjoy, whether that’s mountain biking, long-distance kayaking, ultra-marathoning, or simple hiking — one piece of gear is an essential before all others. Mostly because you need this piece of gear to carry all the others. We’re talking about backpacks.

Outdoor sporting backpacks come in many varieties and with many features, but can be broken down into a few categories: size, main pack features, and extra enhancements.

The first consideration should be the size of your pack. Depending on your chosen activity, you may want more or less carrying capacity — but some activities also have time and distance concerns as well.

Most packs are categorized by volume, measured in liters. Some manufacturers will use cubic inches — 1,000 cubic inches equates to about 16 liters.

The small (0-30 L) category encompasses everything from an afternoon jaunt to a light overnighter. In general, my stance is that it’s better to have a little extra unused space over running out of granola bars halfway through the trip, no matter the duration.

More than an overnighter, less than a thru-hike is really where the medium (30-50 L) category has its sweet spot. Enough space to go beyond the bare necessities for a longer overnight trip, and enough to pack for two to three nights — more if you’re a really efficient packer.

Believe it or not, you can actually buy at least 80-liter backpacks. At a certain point it’s less about how much you can pack at one time than how well you can plan for refuels, but I digress. Suffice to say, you could easily use a large (50+ L) backpack to pack for a 4- to 5-day wilderness getaway.

Keep an eye out for these other features to choose the perfect pack for your particular needs.

Straps are probably the most important part of a pack once you get past what it can carry. This is where price can start to vary widely. You’ll have to decide how much cushion you’re willing to pay for. Either way, make sure that it’s still quality material that is durable and won't easily degrade with repeated use. Some manufacturers will skimp on durability for the illusion of comfort.

The flex and width of a strap is often as important as the padding. Wider shoulder straps will better distribute the weight and will lead to less shoulder and neck pain.

What you want to do may also affect the closure mechanism you want to choose. There are bags with zippers, packs with buckles, clasps or a number of other obscure possibilities. There aren’t any hard-and-fast rules here, but think about what you’ll be doing and how this element might impact the usability.

Will you be wearing gloves a lot of the time when you’re trying to dig around for a tool? Choose an easy-to-open closure such as a buckle that will not hinder you from opening your pack when gloves reduce your manual dexterity. Are you going to be exposed to lots of mud and other elements that could easily find their way into your pack? Go with a zipper closure to ensure that your pack is sealed off from the outside world.

Odds are no matter what you’re doing, you will want to look for some level of water resistance. This can be as hardcore as a 100 percent watertight canoeing pack, which obviously comes with some additional expense, or simply a basic water-repellent fabric cover that can be pulled out during rainy conditions and stowed away in the pack when no longer needed.

Keep in mind that there are additional external attachments that can add versatility and carrying capacity. Strapping gear to the outside of a pack can be an economical way to maximize your carry load while still using a smaller and lighter backpack.

It’s important to note that this is an inherently subjective discussion. Some people simply need more supplies. And some people have physical limitations that require consideration. I myself have back troubles. My preferences is in finding ways to get by with fewer supplies, coupled with a supportive pack.

Once you have chosen all of the main features such as straps and closure mechanisms, it's time to look at some add-ons that will take your pack from basic to practically perfect.

There are also upper-echelon enhancements, like lumbar support, hydration packs, insulated liners — the sky’s the limit.

If you suffer from back pain or if you are carrying a heavy load for long distances (especially for the 30+ L packs), look for a pack with built-in lumbar support. This is often an X-shaped frame that conforms to the natural curve of your spine and works by keeping the pack close to your body and distributing the weight evenly.

Another essential feature for long-distance hikers is a hydration pack, so a backpack with a hydration sleeve is key to securely hold the hydration pack in place.

If you want to keep food cold (or hot) while you carry it, an pack with an insulated liner will be right for you.

The size of a pack is the biggest variable between different types of hiking, but what about other adventures? Well, there are specialized backpacks for running or speed hiking, but basically what you’re looking for are mesh and moisture wicking fabrics with more flexible straps and material. Mountain biking would require a more durable pack, like an external-frame pack, or something streamlined — it depends on your priorities.

At the end of the day, the possibilities are limitless. The best thing to do is make a list of activities you may want to use a pack for, what you’ll need for those particular adventures, and what environmental factors may impact the use of a backpack. From there, you can decide which features are necessities and what is just fluff.