Scientific Anglers- Amplitude Smooth MPX Fly Line

Half size heavy

$99.95

5.00 out of 5

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Built a half-size heavy, the Amplitude Smooth MPX taper starts where the GPX left off. Redesigned with more mass toward the front of the head, the MPX provides the same benefits of the GPX, with an added emphasis on presentation. The power is still there, only with an added bit of finesse. Meet your new best friend.

Free shipping on all United States orders over $50.

SKU: N/A Category: Scientific Anglers Fly Lines Brand: Scientific Anglers

The new Scientific Anglers Amplitude Smooth MPX Fly Line has quickly become one of our best selling floating fly lines.

The Amplitude Smooth series of lines are, simply put, the highest-performance smooth fly lines in the world. With up to five times less drag and eight times the durability of traditional lines, this will change the way you look at fly line performance. Built a half-size heavy, the Amplitude Smooth MPX taper starts where the GPX left off. Redesigned with more mass toward the front of the head, the MPX provides the same benefits of the GPX, with an added emphasis on presentation. The power is still there, only with an added bit of finesse. Meet your new best friend.

Features the revolutionary AST Plus slickness additive for superior shooting ability and increased durability
An excellent general-presentation line for trout, panfish, bass, grayling and carp; also useful for steelhead, salmon, an

d pike.

* Made a half-size heavy to load fast-action rods, but works well with a variety of rod actions
* Best for large dry flies, nymphs, and streamers
* For use in moderate and cold climates
* Braided multifilament core
* SA Line ID
* Improved Dry Tip
* Welded loops at both ends
* SA AMP SMTHMPX WF X F (X = line weight)
* Color is Optic Green/Moss/Buckskin

Scientific Anglers Amplitude Smooth MPX Fly Line- available here in WF4- WF8wt

SA Amplitude Smooth MPX 4wt WF-F
* 30′ Head Weight: 130 grains
* Total Head Weight: 140 grains
* Head Length: 34 feet
* Total Length: 90 feet

SA Amplitude Smooth MPX 5wt WF-F
* 30′ Head Weight: 150 grains
* Total Head Weight: 175 grains
* Head Length: 36 feet
* Total Length: 90 feet

SA Amplitude Smooth MPX 6wt WF-F
* 30′ Head Weight: 175 grains
* Total Head Weight: 210 grains
* Head Length: 38 feet
* Total Length: 90 feet

SA Amplitude Smooth MPX 7wt WF-F
* 30′ Head Weight: 200 grains
* Total Head Weight: 260 grains
* Head Length: 40 feet
* Total Length: 90 feet

SA Amplitude Smooth MPX 8wt WF-F
* 30′ Head Weight: 225 grains
* Total Head Weight: 305 grains
* Head Length: 42 feet
* Total Length: 90 feet

1 review for Scientific Anglers- Amplitude Smooth MPX Fly Line

5 out of 5

David (verified owner) – October 13, 2026

Fly line received and it casts much better than my Orvis kit line. The additional 1/2 weight heavier weight makes it easier to feel your rod load and unload.

I just ordered this fly line and super excited after speaking to the young lady that helped me decide on this product. I’m brand new to this sport and really appreciate the guidance she provided. Wish I remembered her name. Thank you!

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Fly line grain-weight specifications

This is the official AFTMA (American Fishing Tackle Manufacturers Association) chart of fly line grain-weight specifications, based on the front 30 feet of a fly line.

Our website lists the grain weights for each line in its description. Compare that weight with the chart to see whether a particular line is true to size or overweighted.

Weight in grains for the first 30 feet of fly line

Line Weight	Low	Target (in grains)	High
1	54	60	66
2	74	80	86
3	94	100	106
4	114	120	126
5	134	140	146
6	152	160	168
7	177	185	193
8	202	210	218
9	230	240	250
10	270	280	290
11	318	330	342
12	368	380	392
13	435	450	465
14	485	500	515
15	535	550	565

Have more questions? Contact us or watch this video we made explaining the concept:

Free shipping on orders over $50 within the continental US (UPS Ground or USPS). Orders under $50 ship for $7.95.
Faster options: 2-Day and Overnight are available at checkout for an additional charge.
Processing: Orders ship the same day or the next day. You’ll receive a tracking number via email once your package leaves the shop.
Oversized items: Some large or heavy items carry a shipping charge. If so, it’s listed on the product page and added automatically at checkout.
Back-orders: No backorders. If we don't have it, you can't buy it!
International: Canada $29.95 (under 4 lbs) or $49.95 (over 4 lbs). All other countries $49.95 (under 4 lbs) or $69.95 (over 4 lbs).
Sales tax: Applies only to orders shipped within Ohio.

Read our full Shipping Policy

If you need to return an item for any reason:

Simply follow the instructions that are provided with each order.
Send us a quick e-mail, [email protected] and / or drop a note in the return package with the following information: Your name, Order Number, Item(s) and a quick note on reason for returning.

These instructions will also be printed on the return/address form. Please note that if it has been longer than 30 days, we will need to contact you to get a credit card number in order to apply for the credit. Please make sure that we get a good phone number in that case.
Drop the item in the Mail / UPS to us and that’s it – We’ll be looking for it!

We will be waiting for the item and will issue an immediate credit to your credit card account or you may leave the money on the store account for future purchases. If we don’t hear otherwise, the refund will go back on the exact card used for the transaction. *Note: If an item was not purchased via the internet, phone or the purchase was made more than 30 days previous, we will need to contact you to secure a means of credit.

Once we process your return, we will make a note on your “Customer Service Notes” and then drop your return/credit receipt in the mail.
Non-defective, returned merchandise must be in re-sellable condition.
Please make non-defective returns within 30 days of purchase – please contact us if more time has passed.