Police are monitoring a New Zealand website that is selling metal knuckle dusters to gang members.
The weapons are being advertised for sale as an "exclusive" on Facebook page of Motorcycle Clubs New Zealand.
"Ladies something nice for that special man in your life?" the posting asks.
They are being sold for $80 each, with multiple or overseas orders being "welcome and very much encouraged".
Some people living in Australia wrote back saying that they would like to buy some but doubted they would get through Customs.
One potential buyer writes, "I'd like a pair bro, gotta couple of clownz on my list that need the bash."
Another wrote that they "need another set".
However, not everyone was impressed.
One poster wrote: "Buy them for that special guy that will smash you in the face with them ... gees as if there aint enuff weapons to cripple or kill someone with."
Others say, "If you can't win with skin don't raise the fist".
The official definition of an offensive weapon is "anything that can be used to cause injury".
"Police are aware that a New Zealand based Facebook page is currently advertising the sale of knuckle dusters," a police spokesman said.
"Under the Crimes Act, it is an offence to carry an offensive weapon, such as a knuckle duster, without lawful authority or reasonable excuse in a public place."
Customs has previously warned travellers and online shoppers that knuckle dusters, flick knives, daggers, stun guns, or pepper sprays are prohibited or restricted items.
Knuckle dusters are prohibited from importation under the Customs Import Prohibition Order 2011 except with a Consent to Import issued by New Zealand Police.
"Some of these goods can be easily bought in shops and markets overseas or on international websites, but people need to be aware that they are prohibited or restricted in New Zealand and we seize them at the border," a Customs spokesman said.
Importers face charges under the Customs and Excise Act, and the maximum penalty for an individual 'knowingly' importing weapons is six months' imprisonment or up to $10,000 fine.
Sociologist and gang expert Dr Jarrod Gilbert that while such items are often used ornamentally within certain scenes, there is "really only one purpose for knuckle dusters and that's violence".
"That being the case, if a person is caught with one then they'd undoubtedly be charged with carrying an offensive weapon. That being said, I am not aware that they're widely used. If people are going to carry a weapon on them it's more likely to be a knife or worse," he said.
The administrator behind the Motorcycle Clubs New Zealand Facebook page says it was set up "for all MCs and Motorcycle enthusists (sic) in New Zealand".
It encourages people to post club photos and share information but to avoid antagonising other clubs.
Last year, Rotorua man Raymond Ratu failed to argue that a knuckle duster was actually a part of his belt.
He was convicted of possessing an offensive weapon and sentenced to 130 hours of community work.