A jewellery expert has praised the ring and described it as "an uncommon choice" for an engagement.
"You're looking at a centre stone with a cushion cut. It looks as if it could be about 2.5 to 3 carats," said Chris Andrews, a gemologist at Weir and Sons.
"Outside of that, you're looking at two baguette cuts running down the side of it. Outside of that again, there are two diamonds called trilliant cuts.
"They are a triangular cut diamond. It looks to me like there are five stones in total set in either white gold or platinum."
Mr Andrews said that three diamonds or a single one are more common for engagement rings.
"It's an unusual engagement ring. You wouldn't see many with five stones around. You would see a lot more three stones or solitaire," he said.
The couple appear to have expensive taste, with other jewellers estimating the ring could be worth £150,000 (€170,150).
Spencer's brother James is said to have splurged £250,000 (€283,600) for his engagement ring when he popped the question to Pippa Middleton.
The Made In Chelsea star (28) got down on one knee on stage at The Lyceum Theatre in London's West End after the couple watched a performance of The Lion King.
Vogue (32) later took to social media to share her excitement, posting a photo of herself displaying her new ring.
The couple started dating after they met on Channel 4 series The Jump.
The Howth woman said she was very impressed with Spencer's choice in jewellery.
"I can't stop staring. Spencer Matthews, you have found your calling in life. I want you designing all of my jewellery from now on," she said.