Lockdown Needle has many exclusive sizes & grouping types especially when It comes to lining, so below is a short guide explaining the different types to help you choose the perfect needles!
Also named Bugpin Liners, the tightest formation for making super fine, crisp lines. Also used widely for dot-work and stipple shading. The super fine pins are soldered precise and very tightly. 
The industry standard most commonly found type of lining needle, Similar to your standard "Round Liner, RL" but with lockdowns superior quality and precise manufacturing.  
These are perfect for those wanting a slightly bolder, smoother looking line weight and are great for those awkward spots too where a regular liner needle  just doesn't produce a solid looking line. The needle pins soldered a little more openly but with the same precision you are used to with a liner needle. These are our most popular choice and pull lines in the skin like butter! Precise, Bold, Smooth Black lines with ease!
The loose liner produce the most smooth bold lines you can imagine, the pins are soldered in a more loose / open formation but with the same precision you would expect from a liner needle. Similar to the lines you would expect if using a "Round shader, RS" but with the added precision and super sharp, liner pins. Perfect for bold, traditional tattooing! 
The Hollow Liners have rapidly become extremely popular. The needle pins are soldered onto the needle bar without a centre pin in a circular O formation. This gives a very unique feel and line weight. They are real precise, and produce the smoothest, most black lines when healed due to the way the needle is able to hold the ink in the centre. I recommend using a tube size up with these for better ink flow.
Take the regular Hollow needle and solder it much more loosely, as if you were to burn out / spread a regular Hollow Needle. Using this is a totally unique experience that you will love. EFFORTLESSLY bold lines with super low skin trauma due to the forgiveness of the loosely soldered yet precision pins. I recommend using a tube size up with these for better ink flow.