weaver shotgun scope mount. what should i do?

[Real_Hillbilly]

last night i got a weaver shotgun scope mount for 27 dollers for my remington 870 but the only prob was is that my 870 is a 20gage so it said i goen to need to put washers on itand i did but then the mount dont match up with the gun. should i just take this scope back and put the money in to a rifle i am getten? this isent were i got it from but this is what they look like.http://www.gunaccessories.com/Weaver/Convert-A-Mount.asp

i dont realy care for them so what do u all think