The shape disallows the needle grouping from rising up away from the bottom of the tube. Which means that your back handed movement doesn't rob your needle of any ink.
The square cut wash hole HELPS identify the D tip at a glance, plus it is cut low to the tip to improve needle insertion without burring.
D Tip
DT-7$8.50
Replacement Tips
1-3 Round
RT-13R
$5.50
5 Round
RT-5R
$5.50
7-9 Round
RT-79R
$5.50
14 Round
RT-14R
$5.50
1-3 Diamond
RT-13D
$6.00
5 Diamond
RT-5D
$6.00
7-9 Diamond
RT-79D
$6.00
4 Flat - 5 MAG
RT-4F
$6.50
6 Flat - 7 MAG
RT-6F
$6.50
9 MAG
RT-9M
$6.50
7 MAG Shovel
RT-7MS
$6.50
9 MAG Shovel
RT-9MS
$6.50
11 Mag Shovel
RT-11MS
$6.50
13 MAG Shovel
RT-13MS
$6.50
15 MAG Shovel
RT-15MS
$6.50
Tattoo Machine Tube Shanks
Tube Shank
SHK-1$2.00
Time Machine ® Signature Grips For Tattoo Machines
9/16" Knurled
G-1
$8.00
5/8" Knurled
G-2
$9.00
7/8" Knurled
G-4
$10.00
5/8" 6 sided Cyborg
G-3
$10.00
Time Machine ® Delrin Grips
7/8" Knurled Delrin Grips
Get The Size Without The Weight!