This is a multi-centre, randomised, double-blind, double-dummy, two way cross-over, 12 weeks noninferiority study to evaluate the efficacy, safety, and tolerability of FSC 250/50 mcg capsule-based inhaler and a multi-dose inhaler administered BID in adults with COPD. The primary objective of this study is to establish the non-inferiority of the efficacy of the FSC 250/50 mcg capsule-based inhaler compared to the FSC 250/50 mcg multi-dose inhaler administered BID. The study consists of 6 phases: Pre-screening, Screening/Run-in (3 weeks), Treatment Period 1 (12 weeks), Washout (minimum 4 weeks), Treatment Period 2 (12 weeks) and Follow-up (1 week). The total duration of the study for each subject will be at least 32 weeks.