You will need a flowlight adaptor to attach a flowlight to your flowcap. Flowlight adaptors replaced the "bumpers" in previous versions of flowtoys caps in 2014.
If you purchased a flowlight-based prop, your flowcap will include a flowlight adaptor by default.
To attach your flowlight, push the narrow “head” of the flowlight between the “teeth” of the flowlight adaptor inside the flowcap. The flowlight should hang freely and pull all linked lights out of the tube when you remove the cap.
You can find flowcaps with flowlight adaptors on our website here: http://www.flowtoys.com/flowcap/
If you only need a flowlight adaptor, you can find it here: http://www.flowtoys.com/flowlight-adaptor/
If you have any questions, please feel free to contact us!