A standard climbing rope is made of two parts: the dynamic stretchy core, and the colorful protective sheath. (Another term for this is a ”kernmantle” rope, from the German, “kern” = core, “mantle” = sheath.) Andy Kirkpatrick has a memorable way to describe this: The sheath of the rope is like the muscles around your intestines, it holds all the soft inside parts together and protects it.  =^)

Typically, the core and the sheath are manufactured separately and are not connected together. Most of the time this works great, but if the sheath of the rope gets damaged, especially when the rope is under tension, it can separate dramatically, also known as a “core shot”. This can: 1) cause you to wish you brought your brown pants that day, and 2), immediately retire your rope (if you're still alive.)

Thankfully, modern climbing ropes are plenty durable enough in most applications, and we're not hearing about ropes regularly self-destructing. However, there are a few cases where having an extra durable rope can be a good thing:

• single skinny alpine lead ropes

• big walls (more below)

• a remote and longer trip where you need your lead rope to stay in good condition

Solution: a “Unicore” (aka “bonded sheath”) rope, created by the French company Beal around 2012, has the core and sheath glued together. With a Unicore rope, the sheath can get a cut, but the sheath does not separate from the core like with a kernmantle rope, and the rope (probably) remains still usable.

To use another anatomy example, think of it as how your skin is attached to the tissue underneath it.

Beal has a wide variety of ropes available with Unicore technology, from skinny alpine, to sport climbing, to burly big wall 10.5mm. (Some other manufacturers have their own version, such as the Maxim Platinum, Edelwiess Element, and the PMI Extreme Pro. (These companies mentioned Unicore technology, so I don't know if that's under license from Beal, or their own proprietary system.)

Especially for big wall climbing, you want ropes (lead and haul) that are as stout and abuse-resistant as possible. Your partner who's cleaning your pitch will especially appreciate your fine choice of rope, as, they jumar that single strand that’s loaded over an edge thousands of feet off the ground!

Also, in big wall climbing you're using ascenders with teeth on them, which can be especially hard on ropes. 

With a Unicore rope, a small nick does not turn into catastrophic damage, so even if your rope does get slightly cut, you can (usually) continue to climb with it.

The Beal Top Gun Unicore 10.5 / 70 meter would be an excellent choice for your next big wall adventure.

For a more alpine mountaineering type rope, the 9.4 mm Beal Joker Unicore 9.1 would be a good choice. Finally, if you want one of the lightest single ropes available, check out the Beal Opera Unicore 8.5 (which I have and really like). Having the Unicore technology on a small diameter rope can boost your confidence when you see it loaded over an edge . . .

(Reminder: there are no affiliate marketing links or paid product promotions on Alpinesavvy. I’m writing about Unicore ropes because I think they're cool, and providing these links as a courtesy, not because I make many money off it.)

Here's a nice diagram from Beal and the American distributor Liberty Mountain. It shows a few other benefits: you can cut the end of the rope without it getting all fuzzy, it prevents the sheath from slipping, and there is much less water absorption.

Video from Beal on some vicious rope abuse and impressive Unicore results. (Warning, viewer discretion is advised. =^)

Video from PMI with more rope abuse: