Name: MBF2121-10-150
Brand: Monogram

MBF2121-10-150 decoded
Family	Composi-Lok II (Monogram)
Head style	Reduced protruding hex head (source: Monogram drawing MBF2121 Rev U, title block, Table I, material notes)
Nominal diameter	5/16" (-10)
Grip	max grip .150" (grip range .100-.150", MBF2121 Rev U grip table)
Material	A286 CRES. Nut & screw: A286; sleeve: 304 stainless steel

Decoded from the published numbering scheme; not a claim that this exact dash number is a stocked SKU, and not a certified design authority. Always verify against the controlling drawing, spec, and your stress group.

Dimensions

Dimensions as printed, inches
A	Head hex across flats	.437/.429
D	Nut shank diameter	.3115/.3095
G	Max grip + G: datum to the end of the nut shank	.070(ref)
H	Head height	.112/.105
L	Max grip + L: datum to the end of the screw	.89(ref)
Recom. Hole	Drilled hole	.315/.312

All dimensions (19)

B	Head diameter over the hex corners	.479min
E	SLEEVE and SCREW head diameter (2X)	.3110max
F	SCREW wrench flats, on the tail	.152/.147
R	NUT head-to-shank radius	.040max
T	DRIVE NUT hex across flats	.500(ref)
Min Avail. Grip	Min available grip dash	-150
J	Installed blind head diameter	.475min
K	Installed: blind side protrusion	.550max
Break-Off	Screw break-off, measured from the skin surface	+.103/-.000
Tensile	Tensile structural failure, min (lbs)	3600min, lbs
Double Shear	Double shear, min (lbs)	11350min, lbs
Locking Torque	Locking torque, min (in-lbs)	3.5min, in-lbs
Grip limits	Dash 10-150	.100-.150

As printed on MBF2121 Rev U sheet 1 ↗. Letters match the drawing.

Some features are scaled from the figure, not dimensioned.Scaled features

Scaled from the drawing's figure (not drawing dimensions)

Component / feature	Scaled as	Model (in)
NUTnut nose diameter at its end (diameter)	0.768 x D	.2384
NUTnut nose end, from the datum	0.162 x L - G	-.3528
NUTnut bore = screw thread crest diameter (diameter)	0.713 x D	.2214
SCREWscrew thread crest diameter (threads not modelled)	0.713 x D	.2214
SLEEVEsleeve bore over the nut nose and the insert (diameter)	0.839 x D	.2604
SLEEVEsleeve bore beyond the insert (diameter)	0.729 x D	.2264
INSERTinsert outside diameter (= sleeve bore)	0.839 x D	.2604
INSERTinsert inside diameter (= sleeve bore beyond the insert)	0.729 x D	.2264
INSERTinsert end, from the datum	0.368 x L - G	-.5214
SLEEVEcrimp line (start of the crimped band), from the datum	0.724 x L - G	-.8134
SCREWscrew head top (sleeve end), from the datum	0.826 x L - G	-.8977
SCREWscrew head corner radius	0.062 x E	.0192
SLEEVEsleeve top, from the datum (where the scaled nose meets the scaled sleeve bore)	0.112 x L - G	-.3122
NUTnut nose taper (included angle)	angle, as drawn	30.4°
DRIVE NUTdrive nut length	1.064 x T	.5322
DRIVE NUTdrive nut bearing diameter (cone end on the head)	0.684 x T	.3422
DRIVE NUTdrive nut bearing cone (half angle from the axis)	angle, as drawn	30.9°
SCREWscrew tail beyond the drive nut	1.056 x T	.5278
SCREWwrench flats run: tail end to the drive nut (as drawn)	as drawn	.5278

Measured on MBF2121 Rev U sheet 1 figure at 300 dpi and kept as a ratio to a dimension this part number prints. Figure scale 596.5 px/in, fitting row -8, taken from D and E; checked against T (+0.6%), F (+1.2%), L - G (+1.1%), A (end view, across the corners: A / cos 30°) (-4.1%).

Also printed in MBF2121 Rev U for this part

Recommended hole	.312-.315 in (MBF2121 Rev U sheet 1)
Installed blind head	J .475 in min diameter (MBF2121 Rev U sheet 1)
Installed protrusion	K .550 in max (TYPICAL INSTALLATION) (MBF2121 Rev U sheet 1)
Break-off limits	+.103 -.000 in, measured from the skin surface (MBF2121 Rev U sheet 1)
Tensile	3600 lbs min (structural failure) (MBF2121 Rev U sheet 1)
Double shear	11350 lbs min (MBF2121 Rev U sheet 1)
Locking torque	3.5 in-lbs min (MBF2121 Rev U sheet 1)
Min available grip	dash -150 (MBF2121 Rev U sheet 1)
Material and heat treat	NUT & SCREW: A286 PER THE CHEMICAL REQUIREMENTS OF AMS5731, AMS5732, AMS5734 AND AMS5737. HEAT TREATED AS REQUIRED FOR PERFORMANCE. SLEEVE: 304 STAINLESS STEEL PER AMS5639, HEAT TREATED AS REQUIRED FOR PERFORMANCE. INSERT: ACETAL PER ASTM-D4181. DRIVE NUT: MILD STEEL. (MBF2121 Rev U material and finish notes)
Finish	NUT, SCREW & SLEEVE: PASSIVATE PER AMS-QQ-P-35. KAL-GARD ANN-RO #1013, CONVERSION COATING OPTIONAL. INSERT: NONE. DRIVE NUT: CORROSION RESISTANT COATING COLOR BLACK. (MBF2121 Rev U material and finish notes)
Lubricant	DRY FILM LUBE PER MIL-L-46010 TYPE I OR EVERLUBE #812 PER MIL-L-81329, PARAFFIN WAX, OR CETYL ALCOHOL PER MIL-L-87132. (MBF2121 Rev U material and finish notes)

Series and strength (datasheet)

MBF2110 · MBF2111 · MBF2112 · MBF2113 · MBF2120 · MBF2121 · e.g. MBF2112-6-500

Rated shear 75 KSI (catalog comparison chart, MBF2112-06-500); 3/16" (-6) double shear 4,600 lb min, tensile 1,400 lb min, all materials & head styles (MBF2003 Table 10A).

Datasheet (PDF) ↗

Section from Monogram drawing MBF2121 Rev U ↗ sheet 1.Drawing notes

Section drawn from the printed values in Monogram drawing MBF2121 Rev U sheet 1 (blind fastener, reduced protruding hex head). Letters are the drawing's. Manufacturer nominal: printed values, the mean where only two limits are printed. Hex head seen across the corners: outline at the B corner diameter, dashed lines at the A flats. Section through the axis: NUT, SCREW, SLEEVE, INSERT and DRIVE NUT as the drawing names them, each hatched on its own. Max grip .150 plus G .070 and L .89. The drive nut is cut through its hex corners, as the figure draws it; T is across the flats (dashed). Features the drawing shows without a dimension (nut nose, sleeve start and bores, insert, screw thread, screw head length and corner, crimp line, drive nut length and cone, tail length) are scaled from MBF2121 Rev U sheet 1 figure and are not drawing dimensions; the INSERT is all scaled (dashed outline). Threads not modelled.

Model: Monogram drawing MBF2121 Rev U

Envelope model, not manufacturer CAD.Model details

MBF2121-10-150, manufacturer nominal. Simplified component model from Monogram drawing MBF2121 Rev U sheet 1. Manufacturer nominal: printed values, the mean where only two limits are printed. Flush heads hold the printed head angle; the head depth is derived. Not manufacturer CAD. Verify against the current drawing before use. One named solid per component as the drawing calls them out (NUT, SCREW, SLEEVE, INSERT and, where the drawing has one, DRIVE NUT). Features the drawing shows without a dimension are scaled from its figure and listed as scaled in the STEP header; threads are not modelled. Axis +Z, head up, z = 0 at the face the head bears on. STEP (AP214) is in inches; STL has no units and is written in millimetres.

Other head styles, same diameter and grip

MBF2120-10-150 low profile protruding head

MBF2121 grip chart: 5/16" (-10)

32 grips

Every catalogued max-grip dash number at this diameter. Stack thickness must fall inside the fastener's grip range: see the design calculators.

Other diameters at this grip:

MBF2121-5-150 MBF2121-6-150 MBF2121-7-150 MBF2121-8-150 MBF2121-9-150 MBF2121-11-150 MBF2121-12-150

Exploded view of the fastener.US 4,457,652, Composite buckling blind fastener (Pratt), Fig. 6 ↗ · US patent drawingWhy this family: Monogram's US 10,267,347 states: "the original Composi-Lok fastener is described in U.S. Pat. No. 4,457,652" (John D. Pratt, 1984; later assigned to Monogram). Shows the original Composi-Lok, not the Composi-Lok II drive-nut version.

Axial cross-sectional view of the assembled fastener prior to installation. — Exploded view of the fastener.US 4,457,652, Composite buckling blind fastener (Pratt), Fig. 6 ↗ · US patent drawingWhy this family: Monogram's US 10,267,347 states: "the original Composi-Lok fastener is described in U.S. Pat. No. 4,457,652" (John D. Pratt, 1984; later assigned to Monogram). Shows the original Composi-Lok, not the Composi-Lok II drive-nut version.

Install tooling

Install tooling: MP550BFDN-10AA (Monogram MBF2003 Rev AG (Composi-Lok II install spec), p.4, Table 1) · proprietary

MGPCL Protruding head leaf gage (break-off check)
RM3122-10 Removal nose piece module, protruding hex

Composi-Lok II tool tables

Decode details

Decode details
Series	Composi-Lok II
Decode confidence	high
Numbering source	Monogram drawing MBF2121 Rev U, title block, Table I, material notes

Composi-Lok II grips: "incremental 0.050\" grip lengths" (MBF2003 §2.1); the grip dash is the max grip, e.g. -300 covers .250-.300" (MBF2110/2112/2113 drawings, grip table).
Diameter dash per the drawing's basic-dimensions table (e.g. -6 = 3/16").
Suffix "A" "designates dual drive nut system for robotic installation" (MBF2112 drawing note 1); MBF2003's installation tooling "not applicable to Composi-Lok II which have an 'A' suffix" (MBF2003 §1.1).

Government reference cross-reference (DLA FLIS)

not listed under this PN

MBF2121-10-150 is not listed in FLIS under this exact part number (FLIS data as of 2025-03-18, March 2025 snapshot). FLIS may record it with a material or finish code, or under the standard part number.

Source: DLA PUB LOG ↗. Search any part number in the decoder.

Cross-reference MBF2121-10-150

Composi-Lok II by Monogram, blind bolt
Datasheet (PDF) ↗
Manufacturer page ↗
Numbering: Monogram drawing MBF2121 Rev U, title block, Table I, material notes ↗
Geometry: MBF2121 Rev U ↗

Lead-time risk for this family (SpecLok sourcing assessment): High

Supply signal

not in FLIS by this PN; no SpecLok quotes yet

Supply signalfor this part number

Not listed in FLIS under this exact part number (March 2025 snapshot).
No SpecLok quotes yet.

A signal from records SpecLok holds, not availability, stock or a lead-time promise. FLIS lists who has recorded a part number for the item, not who makes it today. DoD awards carry no NSN or part number, so award activity is for the item name's class.

Sources: DLA FLIS Data Electronic Reading Room (PUB LOG) ↗, DLA PUB LOG ↗, USAspending.gov award search API ↗; DoD award data 2025-10-01 to 2026-07-06; compiled 2026-09-28.