Harmonic Hot Tubs Replacement Hot Tub Covers

What size AIRCAP 1™ fits your Harmonic hot tub?

Harmonic Hot Tubs are made by GPM Manufacturing LLC of Franklin, Kentucky, and sold through local dealers. GPM’s other brands include Resort Hot Tubs, Celtic Hot Tubs and Icelandic. Resort’s Premium series shares some shells with Harmonic — the Resort Buxton RP166L, for example, is the same 78" square shell as the H166L — while Celtic’s hot tubs and Icelandic’s square ones use different shells. Harmonic lists fifteen hot tubs, and the seven in our fitter are every square one in the range.

Here is how the 7 Harmonic models in our fitter map to AIRCAP 1™ sizes:

• The H166L and H166L.PP (H166Bpp) each take the AIRCAP 1™ XX-Small, which fits square spas 77–79".
• The H277B and H277L each take the AIRCAP 1™ Small, which fits square spas 83–85".
• The H288B, H288L and H288DL each take the AIRCAP 1™ X-Large, which fits square spas 92–94".

Same size class, same cover. After the first digit (the pump count), a Harmonic model number gives its size class: the H166L and H166L.PP are 6x6 tubs, the H277B and H277L are 7x7, and the H288B, H288L and H288DL are 8x8. In today’s names, the letters give the seating — B for bench, L for lounge, DL for double lounge — and the seating does not change the cabinet: the two 7x7 tubs are different shells on the same 84" x 84" cabinet, and the three 8x8 tubs are three seating layouts on the same 93" x 93" cabinet, so each group takes one cover size. The H166L.PP is the Plug & Play version of the H166L — the same 78" shell, set up for a 120-volt supply — and was first sold as the H166Bpp in 2024, so an H166Bpp takes the same XX-Small.

Comparing figures? Harmonic’s 2024 product pages listed the H277L at 83" x 83" and the H288B and H288L at 92" x 92", and some current product descriptions still repeat those numbers; the 2026 brochure prints 84" and 93". Photos from both years show the same shells, and each pair of figures falls in the same AIRCAP 1™ size, so the Small and X-Large apply either way. The spec table on the H166L product page also shows 77" x 83", a figure copied from the rectangular H167B; the H166L is 78" x 78", as the brochure and the product description both say.

H277B owners: the first H277B, shown in Harmonic’s 2024 photos and in its owner’s manual, has a different interior from the tub pictured here, with two top-load filters on a corner platform where today’s has a fourth corner seat. The cabinet is the same 84" square, so it takes the same Small.

Every AIRCAP 1™ ships with the Ziptech™ modular skirt system, so you can zip on the right skirt depth for your cabinet instead of ordering a custom cover.

Not every Harmonic hot tub takes a square cover. The H167B and H167B.PP (the PP was sold in 2024 as the H167Lpp) are about 77" x 83", the H157L and H157L.PP 58" x 83" (Harmonic listed the H157Lpp at 60" x 84" in 2024), the two-seat H146L.PP 51" x 77" and the ten-seat H2810L 93" x 120" — all rectangles. The H28RB and H28RB Vintage are round, and their 93" is a diameter, not the side of a square. Harmonic sells no swim spas. The AIRCAP 1™ is built for square cabinets from 77 to 94 inches.

Measure your own spa before ordering — cabinet sizes can change between model years. The SureFit™ measuring guide walks through it in two measurements, and works for any hot tub, Harmonic or not.