.dif = differential backup
.fil = filegroup backup
.trn = tranlog backup
as most people follow MS's lead, as they did with .bak, .mdf, .ndf (silly, imo, why not .mdf also???), etc..
SQL DBA,SQL Server MVP(07, 08, 09)[size=2]Prosecutor James Blackburn, in closing argument in the Fatal Vision murders trial: If in the future, you should cry a tear, cry one for them [the murder victims]. If in the future, you should say a prayer, say one for them. And if in the future, you should light a candle, light one for them.[/size]