• 300 mm extension designed to connect core drill bits with 1-1/4 inch thread. • Made of heat-treated industrial 45 steel for greater durability and stability. • Hollow design allows water circulation during wet drilling for cooling and dust removal. • Total length of 300 mm with an effective thread length of 250 mm. • Compatible with drilling work in granite, concrete, glass, and brick. • Effectively increases the working range for deeper drilling. • Compact and lightweight metallic structure, easy to transport and store.