Plain Connecting Pins: This photo illustrates the different sizes of the 3 types of plain connecting pins. The top row is a "chain" of 2 holed 8116 14mm antique green lily octagons held together with P2 pins, the 2nd row is a "chain" of 2 holed 8116 14mm blue violet lily octagons held together with P4 pins and the 3rd row is a "chain" of 2 holed 8116 14mm bordeaux  lily octagons held together with P6 pins and also added is a 50mm 8611 pencil drop. If you will be adding a medium to large size crystal to say, a lily octagon, you might want to use the 14mm size connecting pin to insure that the pin will be long enough to go through the hole in the crystal and still be able to bend the end of the pin to keep the crystal from falling off the pin.