Cross-over joint acts for conversion and connection and it is the basic component in downhole work. It is divided into drill string cross-over joint and tubing cross-over joint. There are A type (same diameter), B type (different diameter) and C type (levoform).

Denotation	Upper Connection Part	Lower ConnectionPart	Type
Kelly Cross-overJoint	Kelly	Drill pipe　joint	Ａ　or B
Drill Pipe Joint	Drill Pipe Joint	Drill Pipe Joint	Ａ　or B
Crossover Joint	Kelly	Drill Collar	Ａ　or B
Drill CollarJoint	Drill Collar	Drill Collar	Ａ　or B
Bit Joint	Drill Collar	Bit	Ａ　or B
Swivel Joint	Swivel Lower Joint	Kelly	C
Fish Joint	Kelly	drill Pipe Joint	C
	Drill Pipe Joint	Fishing Tool	C

External Thread					Internal Thread
Thread Code Name	Tapering	Large End Diameter (mm)	Small End Diameter (mm)	I．D(mm)	Thread Code Name	Tapering	Large End Diameter (mm)	Small End Diameter (mm)	I．D．(mm)
1.900TBG	1: 16	48.3	47	40.3	1.900TBG	1: 16	55.9	66.1	49.9
2-3/8TBG	1: 16	60.3	59	40.3	2-3/8TBG	1: 16	73.0	58.1	61.9
2-7/8TBG	1: 16	73	70	62	2-7/8TBG	1: 16	88.9	70.8	74.6
3-1/2TBG	1: 16	88.9	86	76	3-1/2TBG	1: 16	108.0	86.7	90.5
4TBG	1: 16	101.6	98	88	4TBG	1: 16	120.6	98.5	103.2
4-1/2TBG	1: 16	114.3	111	100.3	4-1/2TBG	1: 16	132.1	111.2	115.9
4-1/2BCSG	1: 16	114.7	112	100	1.900UPTBG	1: 16	63.5	51.0	54.8
1.900UPTBG	1: 16	53.2	51	40.3	2-3/8UPTBG	1: 16	77.8	62.8	67.5
2-3/8UPTBG	1: 16	65.9	64	50.3	2-7/8UPTBG	1: 16	93.2	75.5	80.2
2-7/8UPTBG	1: 16	78.6	76	62	3-1/2UPTBG	1: 16	114.3	92.2	96.9
3-1/2UPTBG	1: 16	95.2	92	75.9	4UPTBG	1: 16	127.0	104.9	109.6
4UPTBG	1: 16	108.0	104	88.6	4-1/2UPTBG	1: 16	141.3	117.6	122.3
4-1/2UPTBG	1: 16	120.6	117	100.3