Phil Mustard hit his second century in as many days to lead Durham to a 59-run Clydesdale Bank 40 Group B victory over Glamorgan at Chester-le-Street.
Mustard took up where he left off in his 143 against Surrey on Saturday by scorching to a 55-ball century, compared with 100 balls for fellow opener Mark Stoneman and 84 for the Dragons' Mark Wallace.
With Gordon Muchall chipping in with 75, Durham amassed 307-2, but the visitors were on target to overhaul them until Wallace fell for 105, his maiden one-day century, before Glamorgan were all out for 248 after 36.2 overs.
Wallace put on 117 in 17 overs for the fourth wicket with Marcus North before driving Chris Rushworth to extra cover with the score on 207 in the 28th over.
Four overs later North holed out to long-on off Gareth Breese for 59, leaving the rest with too much to do. In their frantic chase the Dragons threw wickets away, the remaining five going down for 20 runs.
Breese was the pick of Durham's bowlers with four for 50 while Scott Borthwick and Rushworth also picked up two wickets apiece.
Mustard offered two difficult chances. On 21 he lifted Graham Wagg to deep mid-wicket, where Chris Cooke ran round and got both hands to the ball but tipped it over for six.
Then on 98 Mustard cut seamer John Glover low to backward point's right. Ben Wright got his hand to the ball just above the ground, but a single resulted and Mustard reached three figures with a straight drive later in the over.
The innings was only in the 19th over when he went down the pitch to 19-year-old off-spinner Andrew Salter and was bowled for 107.
Stoneman remained unbeaten on 112, scoring at a run-a-ball just as he had in making 50 against Surrey.
The two wins lifted Durham from next to bottom in their group to third place with two games left.