Think of a great fast bowler and more often than not he'll have a running mate doing his bit at the other end.
Trueman and Statham, Lindwall and Miller, Lillee and Thomson, Ambrose and Walsh, Akram and Younis, McGrath and Gillespie. They all made their mark individually but together they bounced off each other and presented all manner of difficulties for the batsmen.
Dale Steyn and Morne Morkel might not quite be in that highest category. Yet. Give them time, they're 28 and 27 respectively, longtime teammates at Northern Titans and promising to make life exceedingly demanding when the three-test series starts at Dunedin next Wednesday.
They offer differing challenges. Steyn, the world's No 1-ranked test bowler, is slippery, produces late away swing and has the knack of producing skiddy bouncers which are both sharp and more difficult to pick up for a batsman than a more conventional shorter-pitched delivery.
His record speaks for itself: 263 wickets from 51 tests at 23.07. In 62 ODIs, he's taken 91 wickets at 28.31; 21 T20s have produced 29 wickets at 18.31.
Morkel, tall, all arms and pumping knees on his direct approach, is the bounce man, awkward to handle and no slouch in the pace department either.
Yet there is a contrast between his numbers with the white ball and the red. In 36 tests, Morkel has taken 129 wickets at 30.57, which are certainly not numbers to be sniffed at.
However stick a white ball in his hands and there's a change.
In 22 T20s, he's taken 32 wickets at 17.21; in 54 ODIs, 94 at 23.18.
One remarkable point about the pair is neither was rated promising enough to win selection for South Africa at schools level.
In Morkel's mind, any notion of rivalry between the pair is wrong. Work off each other? Certainly, but in the most positive of ways.
"We have played together for the Titans for many years and we're close friends," Morkel said.
"We understand we're going to have more tough days than good days so we now try and support each other and I think that's healthy for the team.
"It goes for every single bowler. We try and lift one another because you don't know when that bad day is around the corner."
Steyn has a sparky personality; Morkel appears more reserved.
"Dale's got a lot of energy and sometimes that gets me fired up," Morkel added. "It's nice when Dale starts off bowling quite quickly and the speed gun shows above 140km/h, and I must admit ... I try to match it," he quipped.
"But Dale is the senior bowler in our team and a guy we all look up to."
Steyn said they put their heads together in assessing opposing batsmen, but only to a point.
"What works for me might not work for Morne, because he's a completely different bowler," Steyn said yesterday.
"But it wouldn't help if I didn't give him some advice on what I thought the batter was going to do."
Now throw in the brisk third cog, Vernon Philander, and the problems for the New Zealand batsmen are compounded. Philander, after an ordinary start to his international career five years ago, climbed into the Australians and Sri Lankans a couple of months ago. He took five wickets in an innings four times in the course of his first three tests and his 30 wickets from four tests have cost a remarkable 13.23 apiece.
Philander, 26, is due in Auckland this weekend, along with legspinner Imran Tahir to round out the first choice South African test attack. Life isn't about to get any easier for New Zealand batsmen.