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Email: Sales@lfoleary.com

Standard L-1, L-2, and Plain Taper Ring

Gage Sizes


1/16-27 NPT 

1/8-27 NPT

1/4-18 NPT

3/8-18 NPT

1/2-14 NPT

3/4-14 NPT


1"-11 1/2 NPT

1" 1/4-11 1/2 NPT

1" 1/2-11 1/2 NPT

2"-11 1/2 NPT

2" 1/2-8 NPT

3"-8 NPT

Standard L-1, L-2, and Plain Taper Ring

Gage Sizes


1/16-27 NPT 

1/8-27 NPT

1/4-18 NPT

3/8-18 NPT

1/2-14 NPT

3/4-14 NPT


1"-11 1/2 NPT

1" 1/4-11 1/2 NPT

1" 1/2-11 1/2 NPT

2"-11 1/2 NPT

2" 1/2-8 NPT

3"-8 NPT

NPTF and ANPT Gage L-1, L-2, and L-3

After using the L-1 gage the L2 ring or L3 plug is assembled with the part and must stop within 1/2 turn plus or minus of where the L1 stopped. The L-2 ring and L-3 plug are designed to clear the threads of the part that the L-1 contacted with and contact with the threads further onto or into the part. This measures the taper of the thread on the part by comparing the front threads and the back threads.If the taper is too severe or too straight, the L-2 ring or L-3 plug will not stop within 1/2 turn from the point where the L-1 stopped. Remember the L2 and L3 are to check taper only not size.

1" 1/2-11 1/2 NPT

2"-11 1/2 NPT

2" 1/2-8 NPT

3"-8 NPT

3" 1/2-8 NPT

4"-8 NPT

5"-8 NPT

6"-8 NPT

Standard L-1 Plug

Gage Sizes


1/16-27 NPT 

1/8-27 NPT

1/4-18 NPT

3/8-18 NPT

1/2-14 NPT

3/4-14 NPT

1"-11 1/2 NPT

1" 1/4-11 1/2 NPT


NPT Working Gage L-1 

The L1 when screwed onto the pipe or plug into the hole "hand tight" should be flush with the end of the pipe or the hole, or gage plane, within 1 turn.

Standard L-1 Ring

Gage Sizes


1/16-27 NPT 

1/8-27 NPT

1/4-18 NPT

3/8-18 NPT

1/2-14 NPT

3/4-14 NPT

1"-11 1/2 NPT

1" 1/4-11 1/2 NPT


1" 1/2-11 1/2 NPT

2"-11 1/2 NPT

2" 1/2-8 NPT

3"-8 NPT

3" 1/2-8 NPT

4"-8 NPT

5"-8 NPT

6"-8 NPT

Glastonbury Southern Gage

Tapered Pipe Thread gages (available in Steel, Chrome, and Carbide) 

Glastonbury Southern Gage manufactures many types of pipe thread gages including, NPT, ANPT, NPTF, BSP and API working gages. Pipe thread gages are used to check the size and taper to ensure proper sealing of the manufactured components when assembled. Pipe gages come in different styles based on what they need to inspect, size or taper.