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Your posting is not clear. Is your DA crank a triple crank, or a 53/39? A short cage RD will handle any 10 speed cassette sold by Shimano or SRAM with a 53/39 (except an 11-28). The only time you push the wrap capacity to the limit would be coupling a 50/34 compact with an 11-26 SRAM cassette. An 11-28 would exceed the short cage wrap capacity and probably require a longer cage RD. The 28T large cog won't be much of an improvement over a 27T and the 11-28 has awful 19-22-24-28 jumps.
As for pricing, you can look up the prices can't you? There are dozens of online stores to choose from.
Your posting is not clear. Is your DA crank a triple crank, or a 53/39? A short cage RD will handle any 10 speed cassette sold by Shimano or SRAM with a 53/39 (except an 11-28). The only time you push the wrap capacity to the limit would be coupling a 50/34 compact with an 11-26 SRAM cassette. An 11-28 would exceed the short cage wrap capacity and probably require a longer cage RD. The 28T large cog won't be much of an improvement over a 27T and the 11-28 has awful 19-22-24-28 jumps.
As for pricing, you can look up the prices can't you? There are dozens of online stores to choose from.
