25.4mm/1" diameter, +17.5mm offset, Centring Accuracy: 1.0mm, 5 arc second accuracy GMP101 mini reflector prism with circular bubble, removable target plate, spike and padded bag Surveying prism with sturdy and long-lasting construction, Ideal for professional surveying applications Mini Prism Fits to GLS11, GLS12, GLS31, GLS101 poles and also suitable for carrier GRT144, GZR3/103 and SNLL321 adapter It is securely mounted on a durable metal holder that can withstand harsh weather conditions. For quick and precise positioning, it comes with a built-in bubble level