Outboard Spider 9 seals are quickly becoming an Ultra4 racing standard. They are selling fantastic since their August debut, so best to continue serving that demand for ALL of our Spider 9s. Now available are Outboard Seals for 4″ Housings, same great product but for 4″ OD tubes. Sometimes it’s the little things. Head to http://www.spidertrax.com/Outboard-Seal-400 for details.