It's what every fashionable cow is wearing - and it could save their lives.
Feral cows on Lantau Island and in Sai Kung are being fitted with light-reflecting collars to improve safety on rural roads after a spate of accidents.
"It's the same reflective material found on workmen," said Kathy Daxon, chairwoman of the Tai O Community Cattle Group.
Group members took matters into their own hands amid what they saw as a lack of concern from police and the Transport Department for the safety of the estimated 1,100 cattle roaming wild.
Animal concern groups have been lobbying for speed cameras, rumble strips and increased police patrols in areas where the cattle roam.
They say speeding motorists are the biggest killers of wild cattle, but complain that police only take action after accidents. The Transport Department says the areas concerned are not suitable for speed cameras.
Stretches of South Lantau Road have been cited as accident black spots, along with Tai Mong Tsai Road and Pak Tam Road in Sai Kung.
In June last year, eight cows were killed in a hit-and-run incident near Tong Fuk on Lantau.
Sarah Wilson, a 49-year-old quantity surveyor, was fined HK$5,000 in May for failing to give information to police regarding the incident. Her car was found nearby with animal fur caught in its damaged bumper.
This year at least 17 more cattle have been killed on Lantau's roads, according to animal welfare campaigner Dina Yang.
The Agriculture, Fisheries and Conservation Department and the police do not keep records of how many cattle are killed or injured by motorists.
So far 13 cows in Lantau and one in Sai Kung have been fitted with the collars. Both the activists and government officials are checking whether the collars are doing any harm. They are not being fitted to young cattle, and are made of a soft material that will not dig into the animals.
"We are happy to see that the community is taking initiatives towards the welfare and safety of stray cattle," a spokesman for the Agriculture, Fisheries and Conservation Department said.
The question is: will it work?
"Will it stop drivers that don't give a damn? Probably not. But others will slow down, as they see the collars and see that people care about them," Daxon said.
Drivers say the cows have been easier to spot.
The fate of the city's feral cattle has long been a bone of contention. Some residents see them as a colourful feature of rural life while others see them as a foul-smelling nuisance.
The government has ruled out killing the animals, but has moved some to keep them away from urban areas and has started a sterilisation programme.