Micro-catheters and embolic agents offer better results in endovascular treatment of brain arteriovenous malformations. Using said micro-catheters and embolic agents generally requires the creating of a plug at the distal-most portion of said micro-catheters which regularly results in suboptimal results. The present invention teaches how to create and use a device which creates a plug downstream of the distal-most portion of said micro-catheters and thereby ameliorates the suboptimal outcomes associated with creating a plug at the distal-most portion of said micro-catheters.