MITAS Slug-Self Sealant Tube – Greater resistance to breaking down – Seal punctures up to 3 mm in size MITAS wheel tubes marked SSS = Slug Self Sealant are heavier but also have a significantly greater resistance to breaking down. Inside the tube is a preventative gel blend of ecological fibres, binders, polymers and curing components that bind and seal punctures up to 3 mm in size.