Glamorgan's chances of reaching the Friends Life t20 quarter-finals disappeared as Gloucestershire Gladiators won by nine wickets in the final Midlands/Wales/West Group match at the SWALEC Stadium.
Chasing 142 to win, Gloucestershire completed a double over Glamorgan with 22 balls to spare on the back of skipper Michael Klinger's 86 from 59 balls, including 11 fours and a six.
The hosts needed to win to qualify for the last eight but it was a disappointing end to their FLt20 campaign after they had triumphed in their opening four games.
Glamorgan, who included former England bowler Simon Jones, were put into bat and could only make 141 for five overs despite Jim Allenby batting through the innings, scoring 85 from 58 balls with four sixes and six fours.
His dominance was highlighted by only two other batsmen - Marcus North and Murray Goodwin - getting into double figures; Allenby was responsible for 10 of the 13 boundaries struck as Glamorgan struggled against a largely inexperienced attack.
Openers Allenby and captain North, who was promoted up the order, gave the home side a useful platform, scoring 41 from the opening six-over powerplay.
But runs dried up as North was bowled by the impressive Benny Howell, leaving Glamorgan 55 for one in the ninth over.
The big-hitting Chris Cooke failed to make his mark as he holed out to deep midwicket for just six and Nathan McCullum was out leg before.
Glamorgan failed to get a boundary from the eighth to the 14th over until Allenby struck his fifth four, which saw him reach his fifty from 42 balls. It was Allenby's third half-century in nine FLt20 matches this season.
Allenby struck a six to bring up the 100 and followed that up with another maximum off the final ball of the innings.
Gloucestershire made a positive start through Klinger and Chris Dent, reaching 18 for nought after the first two overs from Michael Hogan and Allenby.
Klinger and Dent each struck a boundary off Graham Wagg as Gloucestershire reached 32 after four overs.
After Gloucestershire had got to 65 after eight overs, McCullum came into the attack and made the breakthrough as Dent was caught at long-off for 25.
By the halfway stage, Gloucestershire reached 79 for one with 15 coming off the 10th over from Jones.
Klinger went to a 37-ball half-century and Gloucestershire cruised to victory in the 17th over.