51 Type different Screws head. Special Short Shaft and Flex Shaft Most favor to Boat installation. Good Quality Stainless Steel : up to HR56 T3....T10, T15, T20 Philips 001.5, 002.0, 0, 1, 2 Hex M2.5....5.5 Hex 1.0 ... 4.0 - 1.3, 1.5, 2.0, 2.5 * 0.8, 1.5, 2.0 ^ 2.0, 2.3, 2.6 PZ 0, 1 Y 1.5, 2.0, 3.0 H 2.3 O. 1.0