Birthday foiling tried the 115+ and 650 more comfy but not the same speed like 105+ was a bit underpoweret most of the time with 6,9, so maybee not an bad ideal with the 115+ today.
This feature is only available for Premium members. If you are a premium member make sure that you are logged in. You can upgrade to premium member by selecting the DASHBOARD menu item and choose for Premium member.