The heavy duty clamp on Fishing Rod Holder is manufactured with Capron HMGB Nylon for superior structural strength and has a moulded rod gimbal in the shaft base. Both models have an internal diameter of 40mm and its available to suit rails 32mm & 44mm so it can be used for Oceansouth Heavy Duty and normal T-Top's. Note: Suits all the T Tops above but NOT the Deluxe model below.