This analysis aims to assess whether e-cigarette flavours are associated with quitting success or longer term use of e-cigarettes when provided as stop smoking aids in trial contexts. We aim: 1) to investigate whether the effectiveness of using an EC to stop smoking in comparison to smoking cessation pharmacotherapies, non-nicotine EC or behavioural/no support is associated with the flavour of EC used; and 2) to investigate whether the long-term use of study product is associated with the flavour of nicotine EC used in the intervention arm. More detail can be found in the protocol which is freely available on OSF. At time of posting (17 February 2020) analyses have not yet started).