These blocks are made from super strong Delrin also known as Acetal. It is an engineering thermoplastic (Polyoxymethylene) used in precision parts that require high stiffness, low friction and excellent dimensional stability. In other words it will never shrink, expand, crack, twist or warp under any weather conditions and is UV stabilised.

Added to these great qualities is a new spring loaded tongue that never becomes depressed. The tongue will always open when the knob is loosened.

As of Nov 2009 all SDM Dobsonians will feature these innovative pole blocks.