There is plenty to play for as the final round of pool fixtures in this season's Heineken Champions Cup gets under way on Friday.

Twelve more matches across Friday, Saturday and Sunday round off the competition's group phase.

Here is what is at stake - having a calculator nearby might be handy, given the number of permutations at play.

Pool A

Already qualified: Leinster, Sharks, Saracens, Exeter, Edinburgh

Wins for Leinster, Sharks and Saracens in their final pool fixtures will secure home ties for that trio in the next round, which is scheduled for 31 March-2 April.

Of the remaining teams, Exeter are in the strongest position to also lock up home advantage in the last 16. They face Pool A's bottom side Castres at home, with fifth-placed Edinburgh needing to better their result when they face Saracens - or match it but win by a more convincing margin - to overhaul them.

South African side Bulls are almost certain to reach the last 16. They require one point from Friday's match against Lyon to confirm their progression, but only a freak set of results elsewhere would deny them should they fail to do so.

Quins know a win against Sharks on Saturday will be enough to send them through, but defeat would leave them sweating on the results of games elsewhere.

Four other teams - Racing 92, Gloucester, Lyon and Bordeaux-Begles - remain in the hunt for a last-16 place but cannot guarantee a spot based solely on their own result.

Gloucester's hopes rest on avoiding defeat in Bordeaux, matching Lyon's result and bettering what Racing 92 do in their final pool match, given their inferior points difference.

Cherry and Whites head coach George Skivington told BBC Radio Gloucestershire: "This weekend we'd like to be a bit more clinical, we want to be in the game more than we were last weekend [in the 49-14 loss to Leinster].

"The objective is always to win so we go there looking to win, but I think after last weekend the performance is top of the list."

Fixtures

Kick-off times all GMT

Friday, 20 January: Lyon v Bulls (20:00)

Saturday, 21 January: Harlequins v Sharks (13:00), Leinster v Racing 92 (15:15), Bordeaux Begles v Gloucester (15:15), Exeter v Castres (17:30)

Sunday, 22 January: Edinburgh v Saracens (17:30)

Pool B

Already qualified: Toulouse, La Rochelle, Leicester

Defending champions La Rochelle are one of three teams already through to the next stage. They, along with Toulouse and Leicester, have three wins out of three so far and will secure home last-16 ties with further victories.

London Irish and Northampton have been eliminated, with the other seven teams battling for the five remaining qualification spots.

Ospreys and Munster currently occupy a top-eight place in Pool B and will confirm qualification with wins over Leicester and Toulouse respectively.

Sale, in ninth, visit Ulster, in 10th, on Saturday.

Ulster, who will be without their captain Iain Henderson because of concussion, must win to stand any chance of going through, while Sale would almost certainly be eliminated with a defeat.

"We've got one last shot in the competition and we're going to give it our all," said Ulster back-row forward Duane Vermeulen.

Fixtures

Kick-off times all GMT

Friday, 20 January: Leicester v Ospreys (20:00)

Saturday, 21 January: Northampton v La Rochelle (13:00), Stormers v Clermont Auvergne (17:30), Ulster v Sale (20:00)

Sunday, 22 January: Montpellier v London Irish (13:00), Toulouse v Munster (15:15)