Drill pipe

A drill pipe comprising:

• (a) A drill pipe body having a drill pipe body outer diameter and a drill pipe body inner diameter, wherein the drill pipe body outer diameter is from about 5.1-inches to about 5.4-inches and the drill pipe body inner diameter is from about 4.4-inches to about 4.6-inches;
• and
• (b) A tool joint comprising a rotary shoulder box connection, wherein the rotary shoulder connection comprises:
• i. A box connection having a box axis, wherein the box connection has a box outer radius, a box counter bore radius and a box inner radius, and box threads having a box thread form cut along a box taper;
• ii. A pin connection having a pin axis, wherein the pin connection has a pin outer radius, a pin cylinder radius and a pin nose radius, and pin threads having a pin thread form cut along a pin taper to align with the box threads inside the box connection;
• and
• iii. A primary shoulder connection at a first end of the box connection and a first end of the pin connection comprising:
• (1) A primary box shoulder with a first curved profile defined by a primary axial box radius height, a primary box center point, a primary box radius, and one or more of a first flat region at an inner edge of the first curved profile and a first angled flat region at an outer edge of the first curved profile;
• (2) A primary pin shoulder with a second curved profile defined by a primary axial pin radius height, a primary pin center point, a primary pin radius, and one or more of a second flat region at an inner edge of the second curved profile and a third flat region at an outer edge of the second curved profile;
• and
• iv. wherein the primary box shoulder contacts the primary pin shoulder to form a first seal.