Here's a random question - any idea what a rhinoceros horn is worth on the black market?
Try $65,000 per kilogram. In fact, experts say an average sized rhino horn can bring in as much as a quarter of a million dollars.
So, they're pretty valuable - especially in Asian countries, where the horns are often used in traditional medicine.
In Vietnam, demand is huge because it's believed rhino horns help reduce toxins in the body, treat fever and even cure cancer. Rhino horns are said to be more valuable than cocaine there.
As a result, the illegal poaching of rhinos is big business - particularly in South Africa, which has the biggest rhino population in Africa.
The government says nearly 620 rhinos have been killed there, so far this year. That's almost double the number killed in 2010.
Well now, a move to try and stop it. South Africa and Vietnam have signed a deal to crack down on the illegal trade of rhino horns.
Under the deal, both countries say they'll put more policing into the fight and share more information with each other.
They also plan to work together to protect South Africa's biodiversity and enforce international treaties that ban the trade in rhino horn.
And both countries say they'll appoint a co-ordinator to oversee the deal, which will be in place for five years.
Conservation groups are welcoming the deal, with the World Wildlife Fund describing it as "a pivotal moment in efforts to tackle the current rhino poaching crisis".
Richard Thomas, from the wildlife trade monitoring group Traffic, told the BBC, "Its implementation will of course be down to political will but the chances are much better if the orders come from high enough in the government."
The World Wildlife Fund recently put out a report on rhino poaching. It estimated that over the past 10 years, Vietnamese hunters have paid more than $22 million to hunt rhinos in South Africa.
"The continued slaughter is a cause for immense concern," South Africa's environmental minister, Edna Molewa said.
"We believe that this latest development at an international level is crucial for South Africa to effectively deal with the current scourge of poaching, and with the illegal hunting largely driven by the international demand for the rhino horn."